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From:MICROSOFT <secure_(at)_microsoft.com>
Date:08.05.2007
Subject:Microsoft Security Bulletin MS07-027 Cumulative Security Update for Internet Explorer (931768)

Microsoft Security Bulletin MS07-027
Cumulative Security Update for Internet Explorer (931768)
Published: May 8, 2007

Version: 1.0
Summary

Who Should Read this Document: Customers who use Microsoft Windows

Impact of Vulnerability: Remote Code Execution

Maximum Severity Rating: Critical

Recommendation: Customers should apply the update immediately

Security Update Replacement: This bulletin replaces several prior security updates. See the Frequently Asked Questions (FAQ) section of this bulletin for details.

Caveats: Microsoft Knowledge Base Article 931768 documents the currently known issues that customers may experience when they install this security update. The article also documents recommended solutions for these issues. For more information, see Microsoft Knowledge Base Article 931768.

Tested Software and Security Update Download Locations:

Affected Software:


Microsoft Windows 2000 Service Pack 4


Microsoft Windows XP Service Pack 2


Microsoft Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2


Microsoft Windows Server 2003 Service Pack 1 and Microsoft Windows Server 2003 Service Pack 2


Microsoft Windows Server 2003 with SP1 for Itanium-based Systems and Microsoft Windows Server 2003 with SP2 for Itanium-based Systems


Microsoft Windows Server 2003 x64 Edition Service Pack 1 and Microsoft Windows Server 2003 x64 Edition Service Pack 2


Windows Vista


Windows Vista x64 Edition

Tested Microsoft Windows Components:

Affected Components:


Microsoft Internet Explorer 5.01 Service Pack 4 on Windows 2000 Service Pack 4 — Download the update


Microsoft Internet Explorer 6 Service Pack 1 when installed on Windows 2000 Service Pack 4 — Download the update


Microsoft Internet Explorer 6 for Windows XP Service Pack 2 — Download the update


Microsoft Internet Explorer 6 for Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 — Download the update


Microsoft Internet Explorer 6 for Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 — Download the update


Microsoft Internet Explorer 6 for Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems — Download the update


Microsoft Internet Explorer 6 for Windows Server 2003 x64 Edition Service Pack 1 and Windows Server 2003 x64 Edition Service Pack 2 — Download the update


Windows Internet Explorer 7 for Windows XP Service Pack 2 — Download the update


Windows Internet Explorer 7 for Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 — Download the update


Windows Internet Explorer 7 for Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 — Download the update


Windows Internet Explorer 7 for Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 with SP2 for Itanium-based Systems — Download the update


Windows Internet Explorer 7 for Windows Server 2003 x64 Edition Service Pack 1 and Windows Server 2003 x64 Edition Service Pack 2 — Download the update


Windows Internet Explorer 7 in Windows Vista — Download the update


Windows Internet Explorer 7 in Windows Vista x64 Edition — Download the update

The software in this list has been tested to determine whether the versions are affected. Other versions are either past their support life cycle or are not affected. To determine the support life cycle for your product and version, visit the Microsoft Support Lifecycle Web site.
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General Information

Executive Summary

Executive Summary:

This update resolves several newly discovered, privately reported and public vulnerabilities. Each vulnerability is documented in its own subsection in the Vulnerability Details section of this bulletin.

If a user is logged on with administrative user rights, an attacker who successfully exploited the most severe of these vulnerabilities could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with the same user rights as the logged-on user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

We recommend that customers apply the update immediately.

Severity Ratings and Vulnerability Identifiers:
Vulnerability Identifiers Impact of Vulnerability Internet Explorer 5.01 Service Pack 4 on Windows 2000 Service Pack 4 Internet Explorer 6 Service Pack 1 when installed on Windows 2000 Service Pack 4 Internet Explorer 6 for Windows XP Service Pack 2 Internet Explorer 6 for Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 Windows Internet Explorer 7 for Windows XP Service Pack 2 Windows Internet Explorer 7 for Windows Server 2003 Service Pack 1 and Windows Server 2003 Service Pack 2 Windows Internet Explorer 7 in Windows Vista

COM Object Instantiation Memory Corruption Vulnerability - CVE-2007-0942


Remote Code Execution


Critical


Critical


Critical


Moderate


Important


Low


Important

Uninitialized Memory Corruption Vulnerability - CVE-2007-0944


Remote Code Execution


Critical


Critical


Critical


Moderate


None


None


None

Property Memory Corruption Vulnerability - CVE-2007-0945


Remote Code Execution


None


Critical


Critical


Moderate


Critical


Moderate


Critical

HTML Objects Memory Corruption Vulnerabilities - CVE-2007-0946, CVE-2007-0947


Remote Code Execution


None


None


None


None


Important


Moderate


Important

Arbitrary File Rewrite Vulnerability - CVE-2007-2221


Remote Code Execution


Critical


Critical


Critical


Moderate


Critical


Moderate


Critical

Aggregate Severity of All Vulnerabilities





Critical


Critical


Critical


Moderate


Critical


Moderate


Critical

This assessment is based on the types of systems that are affected by the vulnerability, their typical deployment patterns, and the effect that exploiting the vulnerability would have on them.

Note The severity ratings for non-x86 operating system versions map to the x86 operating systems versions as follows:


The Internet Explorer 6 for Windows XP Professional x64 Edition severity rating is the same as the Internet Explorer 6 for Windows XP Service Pack 2 severity rating.


The Internet Explorer 6 for Windows XP Professional x64 Edition Service Pack 2 severity rating is the same as the Internet Explorer 6 for Windows XP Service Pack 2 severity rating.


The Internet Explorer 6 for Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 x64 Edition Service Pack 1 severity rating is the same as the Internet Explorer 6 for Windows Server 2003 Service Pack 1 severity rating.


The Internet Explorer 6 for Windows Server 2003 with SP2 for Itanium-based Systems and Windows Server 2003 x64 Edition Service Pack 2 severity rating is the same as the Internet Explorer 6 for Windows Server 2003 Service Pack 2 severity rating.


The Windows Internet Explorer 7 for Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 severity rating is the same as the Internet Explorer 7 for Windows XP Service Pack 2 severity rating.


The Windows Internet Explorer 7 for Windows Server 2003 with SP1 for Itanium-based Systems and Windows Server 2003 x64 Edition Service Pack 1 severity rating is the same as the Windows Internet Explorer 7 for Windows Server 2003 Service Pack 1 severity rating.


The Windows Internet Explorer 7 for Windows Server 2003 with SP2 for Itanium-based Systems and Windows Server 2003 x64 Edition Service Pack 2 severity rating is the same as the Internet Explorer 7 for Windows Server 2003 Service Pack 2 severity rating.


The Windows Internet Explorer 7 in Windows Vista x64 Edition severity rating is the same as the Windows Internet Explorer 7 in Windows Vista severity rating.
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Frequently Asked Questions (FAQ) Related to This Security Update

Why does this update address several reported security vulnerabilities?
This update contains support for several vulnerabilities because the modifications that are required to address these issues are located in related files. Instead of having to install several updates that are almost the same, customers can install only this update.

What updates does this release replace?
This security update replaces several prior security updates. The most recent security bulletin ID and affected operating systems are listed in the following table.
Bulletin ID Internet Explorer 5.01 Service Pack 4 on Windows 2000 Service Pack 4 Internet Explorer 6 Service Pack 1 when installed on Windows 2000 Service Pack 4 Internet Explorer 6 for Windows XP Service Pack 2 Internet Explorer 6 for Windows Server 2003 and Windows Server 2003 Service Pack 1 Windows Internet Explorer 7 for Windows XP Service Pack 2 Windows Internet Explorer 7 for Windows Server 2003 Service Pack 1 Windows Internet Explorer 7 in Windows Vista

MS07-016


Replaced


Replaced


Replaced


Replaced


Replaced


Replaced


Not applicable

What are the known issues that customers may experience when they install this security update?
Microsoft Knowledge Base Article 931768 documents the currently known issues that customers may experience when they install this security update. The article also documents recommended solutions for these issues. For more information, see Microsoft Knowledge Base Article 931768.

Does this update contain any security-related changes that are not Internet Explorer specific?
Yes. The changes are listed in the “Vulnerability Details” section of this bulletin as the “Arbitrary File Rewrite Vulnerability - CVE-2007-2221”. The Microsoft ActiveX Control discussed there is no longer supported .

Does this update contain any security-related changes to functionality?
Yes. Besides the changes that are listed in the “Vulnerability Details” section of this bulletin, this update includes the following security update:

This update includes killbits that will prevent the following ActiveX controls from being run in Internet Explorer:


This security update sets a killbit for the ActiveX control LaunchApp Software, available from Acer Incorporated. Acer Incorporated has released a security bulletin and an update that addresses a vulnerability in the effected component. For more information and download locations, see the security bulletin from Acer Incorporated. This kill bit is being set at the request of the owner of the ActiveX controls. The class identifier (CLSID) for this ActiveX control is:


{D9998BD0-7957-11D2-8FED-00606730D3AA}


This security update sets a killbit for an ActiveX control developed by Research In Motion (RIM). Research In Motion (RIM) has released a security bulletin and an update that addresses a vulnerability in the effected component. For more information and download locations, see the security bulletin from Research In Motion. This kill bit is being set at the request of the owner of the ActiveX controls. The class identifier (CLSID) for this ActiveX control is:


{1D95A7C7-3282-4DB7-9A48-7C39CE152A19}

Can I use the Microsoft Baseline Security Analyzer (MBSA) to determine whether this update is required?
The following table provides the MBSA detection summary for this security update.
Software MBSA 1.2.1 MBSA 2.0.1

Microsoft Windows 2000 Service Pack 4


Yes


Yes

Microsoft Windows XP Service Pack 2


Yes


Yes

Microsoft Windows XP Professional x64 Edition and Microsoft Windows XP Professional x64 Edition Service Pack 2


No


Yes

Microsoft Windows Server 2003 Service Pack 1 and Microsoft Windows Server 2003 Service Pack 2


Yes


Yes

Microsoft Windows Server 2003 with SP1 for Itanium-based Systems and Microsoft Windows Server 2003 with SP2 for Itanium-based Systems


No


Yes

Microsoft Windows Server 2003 x64 Edition Service Pack 1 and Microsoft Windows Server 2003 x64 Edition Service Pack 2


No


Yes

Windows Vista


No


See Note for Windows Vista below

Windows Vista x64 Edition


No


See Note for Windows Vista below

For more information about MBSA, visit the MBSA Web site. For more information about the software that Microsoft Update and MBSA 2.0 currently do not detect, see Microsoft Knowledge Base Article 895660.

Note for Windows Vista Microsoft does not support installing MBSA 2.0.1 on computers that run Windows Vista, but you may install MBSA 2.0.1 on a supported operating system and then scan the Windows Vista-based computer remotely. For additional information about MBSA support for Windows Vista, visit the MBSA Web site. See also Microsoft Knowledge Base Article 931943: Microsoft Baseline Security Analyzer (MBSA) support for Windows Vista.

For more detailed information, see Microsoft Knowledge Base Article 910723: Summary list of monthly detection and deployment guidance articles.

Can I use Systems Management Server (SMS) to determine whether this update is required?
The following table provides the SMS detection summary for this security update.
Software SMS 2.0 SMS 2003

Microsoft Windows 2000 Service Pack 4


Yes


Yes

Microsoft Windows XP Service Pack 2


Yes


Yes

Microsoft Windows XP Professional x64 Edition and Microsoft Windows XP Professional x64 Edition Service Pack 2


No


Yes

Microsoft Windows Server 2003 Service Pack 1 and Microsoft Windows Server 2003 Service Pack 2


Yes


Yes

Microsoft Windows Server 2003 with Service Pack 1 for Itanium-based Systems and Microsoft Windows Server 2003 with Service Pack 1 for Itanium-based Systems


No


Yes

Microsoft Windows Server 2003 x64 Edition with Service Pack 1 and Microsoft Windows Server 2003 x64 Edition Service Pack 2


No


Yes

SMS 2.0 and SMS 2003 Software Update Services (SUS) Feature Pack can use MBSA 1.2.1 for detection and therefore have the same limitation that is listed earlier in this bulletin related to programs that MBSA 1.2.1 does not detect.

For SMS 2.0, the SMS SUS Feature Pack, which includes the Security Update Inventory Tool (SUIT), can be used by SMS to detect security updates. SMS SUIT uses the MBSA 1.2.1 engine for detection. For more information about SUIT, visit the following Microsoft Web site. For more information about the limitations of SUIT, see Microsoft Knowledge Base Article 306460. The SMS SUS Feature Pack also includes the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications.

For SMS 2003, the SMS 2003 Inventory Tool for Microsoft Updates (ITMU) can be used by SMS to detect security updates that are offered by Microsoft Update and that are supported by Windows Server Update Services. For more information about the SMS 2003 ITMU, visit the following Microsoft Web site. SMS 2003 can also use the Microsoft Office Inventory Tool to detect required updates for Microsoft Office applications.

For more information about SMS, visit the SMS Web site.

For more detailed information, see Microsoft Knowledge Base Article 910723: Summary list of monthly detection and deployment guidance articles.

I am using an older version of the software discussed in this security bulletin; what should I do?
The affected software listed in this bulletin has been tested to determine whether the versions are affected. Other versions are past their support life cycle. To determine the support life cycle for your product and version, visit the Microsoft Support Lifecycle Web site.

It should be a priority for customers who have older versions of the software to migrate to supported versions to prevent potential exposure to vulnerabilities. For more information about the Windows Product Lifecycle, visit the following Microsoft Support Lifecycle Web site. For more information about the extended security update support period for these operating system versions, visit the Microsoft Product Support Services Web site.

Customers who require custom support for older software must contact their Microsoft account team representative, their Technical Account Manager, or the appropriate Microsoft partner representative for custom support options. Customers without an Alliance, Premier, or Authorized Contract can contact their local Microsoft sales office. For contact information, visit the Microsoft Worldwide Information Web site, select the country, and then click Go to see a list of telephone numbers. When you call, ask to speak with the local Premier Support sales manager. For more information, see the Windows Operating System Product Support Lifecycle FAQ.
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Vulnerability Details

COM Object Instantiation Memory Corruption Vulnerability - CVE-2007-0942:

A remote code execution vulnerability exists in the way Internet Explorer instantiates COM objects that are not intended to be instantiated in Internet Explorer. An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially allow remote code execution if a user visited the Web page. An attacker who successfully exploited this vulnerability could take complete control of an affected system.

Mitigating Factors for COM Object Instantiation Memory Corruption Vulnerability - CVE-2007-0942:


In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability In addition, Web sites that accept or host user-provided content, or compromised Web sites and advertisement servers could contain specially crafted content that could exploit this vulnerability. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attacker's Web site.


An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.


By default, all supported versions of Microsoft Outlook and Microsoft Outlook Express open HTML e-mail messages in the Restricted sites zone. The Restricted sites zone helps reduce the number of successful attacks that exploit this vulnerability by preventing Active Scripting and ActiveX controls from being used when reading HTML e-mail. However, if a user clicks on a link within an e-mail, they could still be vulnerable to this issue through the Web-based attack scenario.


By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that have not been added to Internet Explorer Trusted sites zone. See the FAQ subsection of this vulnerability section for more information about Internet Explorer Enhanced Security Configuration.


COM objects not intended to be instantiated in Internet Explorer are not included in the default allow-list for ActiveX controls in Windows Internet Explorer 7. Customers who are running Windows Internet Explorer 7 with default settings are therefore not at risk unless these COM objects have been activated through the ActiveX opt-in feature in the Internet Zone. Customers who are upgrading to Windows Internet Explorer 7 and have enabled these COM objects in previous versions of Internet Explorer will have them enabled in Windows Internet Explorer 7. For more information on the ActiveX Opt-in feature and how to add ActiveX controls to the pre-approved list, see the product documentation.
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Workarounds for COM Object Instantiation Memory Corruption Vulnerability - CVE-2007-0942:

Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.


Configure Internet Explorer to prompt before running ActiveX Controls or disable ActiveX Controls in the Internet and Local intranet security zone

You can help protect against this vulnerability by changing your Internet Explorer settings to prompt before running ActiveX controls. To do this, follow these steps:

1.


In Internet Explorer, click Internet Options on the Tools menu.

2.


Click the Security tab.

3.


Click Internet, and then click Custom Level.

4.


Under Settings, in the ActiveX controls and plug-ins section, under Run ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.

5.


Click Local intranet, and then click Custom Level.

6.


Under Settings, in the ActiveX controls and plug-ins section, under Run ActiveX controls and plug-ins, click Prompt or Disable, and then click OK.

7.


Click OK two times to return to Internet Explorer.

Add sites that you trust to the Internet Explorer Trusted sites zone.

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running ActiveX controls. Many Web sites that are on the Internet or on an intranet use ActiveX to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX controls is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX controls. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.


Set Internet and Local intranet security zone settings to “High” to prompt before running ActiveX Controls and Active Scripting in these zones

You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

1.


On the Internet Explorer Tools menu, click Internet Options.

2.


In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

3.


Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.

Note If no slider is visible, click Default Level, and then move the slider to High.

Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.

Add sites that you trust to the Internet Explorer Trusted sites zone.

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running ActiveX controls. Many Web sites that are on the Internet or on an intranet use ActiveX to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX controls is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX controls. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.


Prevent COM objects from running in Internet Explorer

You can disable attempts to instantiate a COM object in Internet Explorer by setting the kill bit for the control in the registry.

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

For detailed steps that you can use to prevent a control from running in Internet Explorer, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent a COM object from being instantiated in Internet Explorer.

Note The Class Identifiers and corresponding files where the COM objects are contained are documented under “What does the update do?” in the “FAQ for COM Object Instantiation Memory Corruption Vulnerability - CVE-2007-0942” section. Replace {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} below with the Class Identifiers found in this section.

To set the kill bit for a CLSID with a value of {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{ XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX }]
"Compatibility Flags"=dword:00000400

You can apply this .reg file to individual systems by double-clicking it. You can also apply it across domains by using Group Policy. For more information about Group Policy, visit the following Microsoft Web sites:

Group Policy collection

What is Group Policy Object Editor?

Core Group Policy tools and settings

Note You must restart Internet Explorer for your changes to take effect.

Impact of Workaround: There is no impact as long as the COM object is not intended to be used in Internet Explorer.
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FAQ for COM Object Instantiation Memory Corruption Vulnerability - CVE-2007-0942:

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data.

What causes the vulnerability?
When Internet Explorer tries to instantiate certain COM objects as ActiveX controls, the COM objects may corrupt the system state in such a way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.

I am running Windows Internet Explorer 7. Does this mitigate this vulnerability?
Yes. Customers who are running Windows Internet Explorer 7 with default settings, are not at risk unless these COM objects have been activated through the ActiveX opt-in feature in the Internet Zone. Customers who are upgrading to Windows Internet Explorer 7 and have enabled these COM objects in previous versions of Internet Explorer will have them enabled in Windows Internet Explorer 7. For more information on the ActiveX Opt-in feature and how to add ActiveX controls to the pre-approved list, see the product documentation.

Windows Internet Explorer 7 in Windows Vista is not affected by this vulnerability.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which means that nearly all pre-installed ActiveX controls are off by default. Users are prompted by the Information Bar before they can instantiate a previously installed ActiveX control that has not yet been used on the Internet. This enables a user to permit or deny access on a control-by-control basis. For more information about this and other new features, see the Windows Internet Explorer 7 features page.

I am running Internet Explorer on Windows Server 2003. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that have not been added to Internet Explorer Trusted sites zone. See the next FAQ in this section for more information about Internet Explorer Enhanced Security Configuration.

What is Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of preconfigured Internet Explorer settings that reduce the likelihood of a user or administrator downloading and running malicious Web content on a server. Internet Explorer Enhanced Security Configuration reduces this threat by modifying numerous security-related settings, including Security and Advanced tab settings in Internet Options. Some of the key modifications include:


Security level for the Internet zone is set to High. This setting disables scripts, ActiveX components, Microsoft virtual machine (Microsoft VM) HTML content, and file downloads.


Automatic detection of intranet sites is disabled. This setting assigns all intranet Web sites and all Universal Naming Convention (UNC) paths that are not explicitly listed in the Local intranet zone to the Internet zone.


Install on Demand and non-Microsoft browser extensions are disabled. This setting prevents Web pages from automatically installing components and prevents non-Microsoft extensions from running.


Multimedia content is disabled. This setting prevents music, animations, and video clips from running.

For more information regarding Internet Explorer Enhanced Security Configuration, please consult the Managing Internet Explorer Enhanced Security Configuration guide, which can be found at the following Web site.

What does the update do?
Because not all COM objects are designed to be accessed through Internet Explorer, this update sets the kill bit for a list of Class Identifiers (CLSIDs) for COM objects that have been found to exhibit similar behavior to the COM Object Instantiation Memory Corruption Vulnerability that is addressed in Microsoft Security Bulletin MS05-054. To help protect customers, this update prevents these CLSIDs from being instantiated in Internet Explorer. For more information about kill bits, see Microsoft Knowledge Base Article 240797.

The Class Identifiers and corresponding files where the COM objects are contained are as follows:
Class Identifier File

BE4191FB-59EF-4825-AEFC-109727951E42


chtskdic.dll

When this security bulletin was issued, had this vulnerability been publicly disclosed?
Yes. This vulnerability has been publicly disclosed. It has been assigned Common Vulnerability and Exposure number CVE-2007-0942.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
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Uninitialized Memory Corruption Vulnerability - CVE-2007-0944:

A remote code execution vulnerability exists in the way Internet Explorer accessing a object when it is not initiated or already deleted. An attacker could exploit the vulnerability by constructing a specially crafted Web page. If a user viewed the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could take complete control of an affected system.

Mitigating Factors for Uninitialized Memory Corruption Vulnerability - CVE-2007-0944:


In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attacker's Web site.


An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.


The Restricted sites zone helps reduce attacks that could try to exploit this vulnerability by preventing Active Scripting from being used when reading HTML e-mail messages. However, if a user clicks a link in an e-mail message, the user could still be vulnerable to this issue through the Web-based attack scenario.


By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that have not been added to Internet Explorer Trusted sites zone. See the FAQ section of this security update for more information about Internet Explorer Enhanced Security Configuration.
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Workarounds for Uninitialized Memory Corruption Vulnerability - CVE-2007-0944:

Microsoft has tested the following workarounds. Although these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.


Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone

You can help protect against this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:

1.


In Internet Explorer, click Internet Options on the Tools menu.

2.


Click the Security tab.

3.


Click Internet, and then click Custom Level.

4.


Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

5.


Click Local intranet, and then click Custom Level.

6.


Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

7.


Click OK two times to return to Internet Explorer.

Note Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly.

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.


Set Internet and Local intranet security zone settings to “High” to prompt before running ActiveX Controls and Active Scripting in these zones

You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

1.


On the Internet Explorer Tools menu, click Internet Options.

2.


In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

3.


Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.

Note If no slider is visible, click Default Level, and then move the slider to High.

Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX Controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX Controls or Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.
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FAQ for Uninitialized Memory Corruption Vulnerability - CVE-2007-0944:

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data.

What causes the vulnerability?
Internet Explorer attempts to access an object which has been deleted. As a result, memory may be corrupted in such a way that an attacker could execute arbitrary code in the context of the logged-in user.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited these vulnerabilities could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit these vulnerabilities through Internet Explorer and then convince a user to visit the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger message that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from these vulnerabilities.

I am running Internet Explorer on Windows Server 2003. Does this mitigate these vulnerabilities?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that have not been added to Internet Explorer Trusted sites zone.

What is the Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of preconfigured Internet Explorer settings that reduce the likelihood of a user or of an administrator downloading and running specially crafted Web content on a server. Internet Explorer Enhanced Security Configuration reduces this risk by modifying many security-related settings. This includes the settings on the Security tab and the Advanced tab in the Internet Options dialog box. Some of the important modifications include the following:


Security level for the Internet zone is set to High. This setting disables scripts, ActiveX controls, Microsoft Java Virtual Machine (MSJVM), and file downloads.


Automatic detection of intranet sites is disabled. This setting assigns all intranet Web sites and all Universal Naming Convention (UNC) paths that are not explicitly listed in the Local intranet zone to the Internet zone.


Install On Demand and non-Microsoft browser extensions are disabled. This setting prevents Web pages from automatically installing components and prevents non-Microsoft extensions from running.


Multimedia content is disabled. This setting prevents music, animations, and video clips from running.

For more information regarding Internet Explorer Enhanced Security Configuration, see the guide, Managing Internet Explorer Enhanced Security Configuration, at the following Web site.

I am running Windows Internet Explorer 7. Does this mitigate this vulnerability?
Yes. Customers who are running Windows Internet Explorer 7 with default settings, are not at risk unless these COM objects have been activated through the ActiveX opt-in feature in the Internet Zone. Customers who are upgrading to Windows Internet Explorer 7 and have enabled these COM objects in previous versions of Internet Explorer will have them enabled in Windows Internet Explorer 7. For more information on the ActiveX Opt-in feature and how to add ActiveX controls to the pre-approved list, see the product documentation.

Windows Internet Explorer 7 in Windows Vista is not affected by this vulnerability.

What is the ActiveX opt-in feature in Windows Internet Explorer 7?
Windows Internet Explorer 7 includes an ActiveX opt-in feature, which means that nearly all pre-installed ActiveX controls are off by default. Users are prompted by the Information Bar before they can instantiate a previously installed ActiveX control that has not yet been used on the Internet. This enables a user to permit or deny access on a control-by-control basis. For more information about this and other new features, see the Windows Internet Explorer 7 features page.

What does the update do?
The update removes the vulnerability by modifying the way that Internet Explorer handles errors when calls are made to objects that are no longer initialized.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
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Property Memory Corruption Vulnerability - CVE-2007-0945:

A remote code execution vulnerability exists in the way Internet Explorer handles a property method. An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially allow remote code execution if a user viewed the Web page. An attacker who successfully exploited this vulnerability could take complete control of an affected system.

Mitigating Factors for Property Type Memory Corruption Vulnerability - CVE-2007-0945:


In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or instant messenger message that takes users to the attacker's Web site.


An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.


By default, all supported versions of Microsoft Outlook and Microsoft Outlook Express open HTML e-mail messages in the Restricted sites zone. The Restricted sites zone helps reduce the number of successful attacks that exploit this vulnerability by preventing Active Scripting and ActiveX controls from being used when reading HTML e-mail. However, if a user clicks on a link within an e-mail they could still be vulnerable to this issue through the Web-based attack scenario.

It cannot be ruled out that this vulnerability could be used in an exploit without Active Scripting. However, using Active Scripting significantly increases the chances of a successful exploit. As a result, this vulnerability has been given a severity rating of Critical on Windows Server 2003.


Microsoft Internet Explorer 5.01 Service Pack 4 on Windows 2000 Service Pack 4 is not affected by this vulnerability.
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Workarounds for Property Memory Corruption Vulnerability - CVE-2007-0945:

Microsoft has tested the following workarounds. Although these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.


Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone

You can help protect against this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:

1.


In Internet Explorer, click Internet Options on the Tools menu.

2.


Click the Security tab.

3.


Click Internet, and then click Custom Level.

4.


Under Settings, in the Scripting section, under Active Scripting, click Promptor Disable, and then click OK.

5.


Click Local intranet, and then click Custom Level.

6.


Under Settings, in the Scripting section, under Active Scripting, click Promptor Disable, and then click OK.

7.


Click OK two times to return to Internet Explorer.

Note Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly.

Add sites that you trust to the Internet Explorer Trusted sites zone.

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.


Set Internet and Local intranet security zone settings to “High” to prompt before running ActiveX Controls and Active Scripting in these zones

You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls and Active Scripting. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

1.


On the Internet Explorer Tools menu, click Internet Options.

2.


In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

3.


Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.

Note If no slider is visible, click Default Level, and then move the slider to High.

Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.

Add sites that you trust to the Internet Explorer Trusted sites zone.

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX Controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX Controls or Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”
Top of sectionTop of section

FAQ for Property Memory Corruption Vulnerability - CVE-2007-0945:

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data.

What causes the vulnerability?
When Internet Explorer calls the property method it may corrupt memory in such a way that an attacker could execute arbitrary code.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited these vulnerabilities could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit the vulnerability and then convince a user to view the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger message that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
This vulnerability requires a user to be logged on and visiting a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.

I am running Internet Explorer on Windows Server 2003. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that have not been added to Internet Explorer Trusted sites zone. See the next FAQ in this section for more information about Internet Explorer Enhanced Security Configuration.

Note It cannot be ruled out that this vulnerability could be used in an exploit without Active Scripting. However, using Active Scripting significantly increases the chances of a successful exploit. As a result, this vulnerability has been given a severity rating of Critical on Windows Server 2003.

What is the Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of preconfigured Internet Explorer settings that reduce the likelihood of a user or of an administrator downloading and running specially crafted Web content on a server. Internet Explorer Enhanced Security Configuration reduces this risk by modifying many security-related settings. This includes the settings on the Security tab and the Advanced tab in the Internet Options dialog box. Some of the important modifications include the following:


Security level for the Internet zone is set to High. This setting disables scripts, ActiveX controls, Microsoft Java Virtual Machine (MSJVM), and file downloads.


Automatic detection of intranet sites is disabled. This setting assigns all intranet Web sites and all Universal Naming Convention (UNC) paths that are not explicitly listed in the Local intranet zone to the Internet zone.


Install On Demand and non-Microsoft browser extensions are disabled. This setting prevents Web pages from automatically installing components and prevents non-Microsoft extensions from running.


Multimedia content is disabled. This setting prevents music, animations, and video clips from running.

For more information regarding Internet Explorer Enhanced Security Configuration, see the guide, Managing Internet Explorer Enhanced Security Configuration, at the following Web site.

What does the update do?
The update removes the vulnerability by modifying the way that Internet Explorer handles the property method.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
Top of sectionTop of section
Top of sectionTop of section

HTML Objects Memory Corruption Vulnerabilities - CVE-2007-0946, CVE-2007-0947:

Several remote code execution vulnerabilities exist in Internet Explorer due to attempts to access uninitialized memory in certain situations. An attacker could exploit these vulnerabilities by constructing a specially crafted Web page. If a user viewed the Web page, these vulnerabilities could allow remote code execution. An attacker who successfully exploited these vulnerabilities could take complete control of an affected system.

Mitigating Factors for HTML Objects Memory Corruption Vulnerabilities - CVE-2007-0946, CVE-2007-0947:


In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit these vulnerabilities. In addition, compromised Web sites and Web sites that accept or host user-provided content or advertisements could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attacker's Web site.


An attacker who successfully exploited these vulnerabilities could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.


By default, all supported versions of Microsoft Outlook and Microsoft Outlook Express open HTML e-mail messages in the Restricted sites zone. The Restricted sites zone helps reduce the number of successful attacks that exploit these vulnerabilities by preventing Active Scripting and ActiveX controls from being used when reading HTML e-mail. However, if a user clicks on a link within an e-mail they could still be vulnerable to this issue through the Web-based attack scenario.

It cannot be ruled out that these vulnerabilities could be used in an exploit without Active Scripting. However, using Active Scripting significantly increases the chances of a successful exploit. As a result, these vulnerabilities have been given a severity rating of Critical on Windows Server 2003.
Top of sectionTop of section

Workarounds for HTML Objects Memory Corruption Vulnerability - CVE-2007-0946, CVE-2007-0947:

Microsoft has tested the following workarounds. Although these workarounds will not correct the underlying vulnerabilities, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.


Configure Internet Explorer to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone

You can help protect against this vulnerability by changing your settings to prompt before running Active Scripting or to disable Active Scripting in the Internet and Local intranet security zone. To do this, follow these steps:

1.


In Internet Explorer, click Internet Options on the Tools menu.

2.


Click the Security tab.

3.


Click Internet, and then click Custom Level.

4.


Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

5.


Click Local intranet, and then click Custom Level.

6.


Under Settings, in the Scripting section, under Active Scripting, click Prompt or Disable, and then click OK.

7.


Click OK two times to return to Internet Explorer.

Note Disabling Active Scripting in the Internet and Local intranet security zones may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly.

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running Active Scripting. Many Web sites that are on the Internet or on an intranet use Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use Active Scripting to provide menus, ordering forms, or even account statements. Prompting before running Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.


Set Internet and Local intranet security zone settings to “High” to prompt before running ActiveX Controls and Active Scripting in these zones

You can help protect against this vulnerability by changing your settings for the Internet security zone to prompt before running ActiveX controls. You can do this by setting your browser security to High.

To raise the browsing security level in Microsoft Internet Explorer, follow these steps:

1.


On the Internet Explorer Tools menu, click Internet Options.

2.


In the Internet Options dialog box, click the Security tab, and then click the Internet icon.

3.


Under Security level for this zone, move the slider to High. This sets the security level for all Web sites you visit to High.

Note If no slider is visible, click Default Level, and then move the slider to High.

Note Setting the level to High may cause some Web sites to work incorrectly. If you have difficulty using a Web site after you change this setting, and you are sure the site is safe to use, you can add that site to your list of trusted sites. This will allow the site to work correctly even with the security setting set to High.

Add sites that you trust to the Internet Explorer Trusted sites zone

After you set Internet Explorer to require a prompt before it runs ActiveX controls and Active Scripting in the Internet zone and in the Local intranet zone, you can add sites that you trust to the Internet Explorer Trusted sites zone. This will allow you to continue to use trusted Web sites exactly as you do today, while helping to protect you from this attack on untrusted sites. We recommend that you add only sites that you trust to the Trusted sites zone.

To do this, follow these steps:

1.


In Internet Explorer, click Tools, click Internet Options, and then click the Security tab.

2.


In the Select a Web content zone to specify its current security settings box, click Trusted Sites, and then click Sites.

3.


If you want to add sites that do not require an encrypted channel, click to clear the Require server verification (https:) for all sites in this zone check box.

4.


In the Add this Web site to the zone box, type the URL of a site that you trust, and then click Add.

5.


Repeat these steps for each site that you want to add to the zone.

6.


Click OK two times to accept the changes and return to Internet Explorer.

Note Add any sites that you trust not to take malicious action on your computer. Two in particular that you may want to add are "*.windowsupdate.microsoft.com" and “*.update.microsoft.com” (without the quotation marks). These are the sites that will host the update, and it requires an ActiveX Control to install the update.

Impact of Workaround: There are side effects to prompting before running ActiveX Controls and Active Scripting. Many Web sites that are on the Internet or on an intranet use ActiveX or Active Scripting to provide additional functionality. For example, an online e-commerce site or banking site may use ActiveX Controls to provide menus, ordering forms, or even account statements. Prompting before running ActiveX Controls or Active Scripting is a global setting that affects all Internet and intranet sites. You will be prompted frequently when you enable this workaround. For each prompt, if you feel you trust the site that you are visiting, click Yes to run ActiveX Controls or Active Scripting. If you do not want to be prompted for all these sites, use the steps outlined in "Add sites that you trust to the Internet Explorer Trusted sites zone”.
Top of sectionTop of section

FAQ for HTML Objects Memory Corruption Vulnerability - CVE-2007-0946, CVE-2007-0947:

What is the scope of the vulnerabilities?
These are remote code execution vulnerabilities. An attacker who successfully exploited these vulnerabilities could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data.

What causes the vulnerability?
Internet Explorer attempts to access uninitialized memory. As a result, memory may be corrupted in such a way that an attacker could execute arbitrary code in the context of the logged-in user.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited these vulnerabilities could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit these vulnerabilities through Internet Explorer and then convince a user to view the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit these vulnerabilities. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger message that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
These vulnerabilities require that a user is logged on and visits a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from these vulnerabilities.

I am running Internet Explorer on Windows Server 2003. Does this mitigate these vulnerabilities?
Yes. By default, Internet Explorer on Windows Server 2003 runs in a restricted mode that is known as Enhanced Security Configuration. This mode sets the security level for the Internet zone to High. This is a mitigating factor for Web sites that have not been added to Internet Explorer Trusted sites zone.

Note It cannot be ruled out that these vulnerabilities could be used in an exploit without Active Scripting. However, using Active Scripting significantly increases the chances of a successful exploit. As a result, this vulnerability has been given a severity rating of Critical on Windows Server 2003.

What is the Internet Explorer Enhanced Security Configuration?
Internet Explorer Enhanced Security Configuration is a group of preconfigured Internet Explorer settings that reduce the likelihood of a user or of an administrator downloading and running specially crafted Web content on a server. Internet Explorer Enhanced Security Configuration reduces this risk by modifying many security-related settings. This includes the settings on the Security tab and the Advanced tab in the Internet Options dialog box. Some of the important modifications include the following:


Security level for the Internet zone is set to High. This setting disables scripts, ActiveX controls, Microsoft Java Virtual Machine (MSJVM), and file downloads.


Automatic detection of intranet sites is disabled. This setting assigns all intranet Web sites and all Universal Naming Convention (UNC) paths that are not explicitly listed in the Local intranet zone to the Internet zone.


Install On Demand and non-Microsoft browser extensions are disabled. This setting prevents Web pages from automatically installing components and prevents non-Microsoft extensions from running.


Multimedia content is disabled. This setting prevents music, animations, and video clips from running.

For more information regarding Internet Explorer Enhanced Security Configuration, see the guide, Managing Internet Explorer Enhanced Security Configuration, at the following Web site.

What does the update do?
The update removes the vulnerabilities by modifying the way that Internet Explorer handles the error resulting in the exploitable condition.

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about these vulnerabilities through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that these vulnerabilities had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.
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Arbitrary File Rewrite Vulnerability - CVE-2007-2221:

A remote code execution vulnerability exists in a media service component that was never supported in Internet Explorer. An attacker could exploit the vulnerability by constructing a specially crafted Web page that could potentially allow remote code execution if a user visited the Web page. An attacker who successfully exploited this vulnerability could take complete control of an affected system.

Mitigating Factors for Arbitrary File Rewrite Vulnerability - CVE-2007-2221:


In a Web-based attack scenario, an attacker could host a Web site that contains a Web page that is used to exploit this vulnerability In addition, Web sites that accept or host user-provided content, or compromised Web sites and advertisement servers could contain specially crafted content that could exploit this vulnerability. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or Instant Messenger message that takes users to the attacker's Web site.


An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.


COM objects not intended to be instantiated in Internet Explorer are not included in the default allow-list for ActiveX controls in Windows Internet Explorer 7. Customers who are running Windows Internet Explorer 7 with default settings are therefore not at risk unless these COM objects have been activated through the ActiveX opt-in feature in the Internet Zone. Customers who are upgrading to Windows Internet Explorer 7 and have enabled these COM objects in previous versions of Internet Explorer will have them enabled in Windows Internet Explorer 7. For more information on the ActiveX Opt-in feature and how to add ActiveX controls to the pre-approved list, see the product documentation.
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Workarounds for Arbitrary File Rewrite Vulnerability - CVE-2007-2221:

Microsoft has tested the following workarounds. While these workarounds will not correct the underlying vulnerability, they help block known attack vectors. When a workaround reduces functionality, it is identified in the following section.


Prevent objects from running in Internet Explorer

You can disable attempts to instantiate a COM object in Internet Explorer by setting the kill bit for the control in the registry.

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

For detailed steps that you can use to prevent a control from running in Internet Explorer, see Microsoft Knowledge Base Article 240797. Follow these steps in this article to create a Compatibility Flags value in the registry to prevent a COM object from being instantiated in Internet Explorer.

Note The Class Identifiers and corresponding files where the COM objects are contained are documented under “What does the update do?” in the “FAQ for Arbitrary File Rewrite Vulnerability - CVE-2007-2221” section. Replace {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX} below with the Class Identifiers found in this section.

To set the kill bit for a CLSID with a value of {XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}, paste the following text in a text editor such as Notepad. Then, save the file by using the .reg file name extension.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{ XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX }]
"Compatibility Flags"=dword:00000400

You can apply this .reg file to individual systems by double-clicking it. You can also apply it across domains by using Group Policy. For more information about Group Policy, visit the following Microsoft Web sites:

Group Policy collection

What is Group Policy Object Editor?

Core Group Policy tools and settings

Note You must restart Internet Explorer for your changes to take effect.

Impact of Workaround: There is no impact as long as the COM object is not intended to be used in Internet Explorer.


Uninstall Windows Media Server 4.1

Remove Windows Media Server 4.1 from systems that it is not intended to run on

Impact of Workaround: Windows Media Server 4.1 functionality will no longer be accessible
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FAQ for Arbitrary File Rewrite Vulnerability - CVE-2007-2221:

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could remotely take complete control of an affected system. An attacker could then install programs; view, change, or delete data.

What causes the vulnerability?
An arbitrary file rewrite vulnerability exist in the control named "mdsauth.dll" of Microsoft Windows Media Server.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as the local user. Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights.

How could an attacker exploit the vulnerability?
An attacker could host a specially crafted Web site that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the Web site. This can also include Web sites that accept user-provided content or advertisements, Web sites that host user-provided content or advertisements, and compromised Web sites. These Web sites could contain specially crafted content that could exploit this vulnerability. In all cases, however, an attacker would have no way to force users to visit these Web sites. Instead, an attacker would have to convince users to visit the Web site, typically by getting them to click a link in an e-mail message or in an Instant Messenger request that takes users to the attacker's Web site. It could also be possible to display specially crafted Web content by using banner advertisements or by using other methods to deliver Web content to affected systems.

What systems are primarily at risk from the vulnerability?
This vulnerability requires that a user be logged on and visit a Web site for any malicious action to occur. Therefore, any systems where Internet Explorer is used frequently, such as workstations or terminal servers, are at the most risk from this vulnerability.

What does the update do?
This update sets the kill bit for a list the Class Identifier (CLSIDs)

The Class Identifies and corresponding files are as follows:
Class Identifier File

D4FE6227-1288-11D0-9097-00AA004254A0


msauth.dll

When this security bulletin was issued, had this vulnerability been publicly disclosed?
No. Microsoft received information about this vulnerability through responsible disclosure.

When this security bulletin was issued, had Microsoft received any reports that this vulnerability was being exploited?
No. Microsoft had not received any information to indicate that this vulnerability had been publicly used to attack customers and had not seen any examples of proof of concept code published when this security bulletin was originally issued.

Acknowledgments

Microsoft thanks the following for working with us to help protect customers:


TippingPoint and the Zero Day Initiative for reporting the Uninitialized Memory Corruption Vulnerability – (CVE-2007-0944).


JJ Reyes of Secunia Research for reporting the HTML Objects Memory Corruption Vulnerability – (CVE-2007-0947).


cocoruder of Fortinet Security Research for reporting the Arbitrary File Rewrite Vulnerability – (CVE-2007-2221).


Disclaimer:

The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

Revisions:


V1.0 (May 8, 2007): Bulletin published.

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