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HistoryJul 29, 2009 - 12:00 a.m.

Microsoft Security Bulletin MS09-034 - Critical Cumulative Security Update for Internet Explorer (972260)

2009-07-2900:00:00

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Microsoft Security Bulletin MS09-034 - Critical
Cumulative Security Update for Internet Explorer (972260)
Published: July 28, 2009

Version: 1.0
General Information
Executive Summary

This security update is being released out of band in conjunction with Microsoft Security Bulletin MS09-035, which describes vulnerabilities in those components and controls that have been developed using vulnerable versions of the Microsoft Active Template Library (ATL). As a defense-in-depth measure, this Internet Explorer security update helps mitigate known attack vectors within Internet Explorer for those components and controls that have been developed with vulnerable versions of ATL as described in Microsoft Security Advisory (973882) and Microsoft Security Bulletin MS09-035.

This security update also resolves three privately reported vulnerabilities in Internet Explorer. These vulnerabilities could allow remote code execution if a user views a specially crafted Web page using Internet Explorer. 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.

This security update is rated Critical for Internet Explorer 5.01 and Internet Explorer 6 Service Pack 1, running on supported editions of Microsoft Windows 2000; Critical for Internet Explorer 6, Internet Explorer 7, and Internet Explorer 8 running on supported editions of Windows XP; Critical for Internet Explorer 7 and Internet Explorer 8 running on supported editions of Windows Vista; Moderate for Internet Explorer 6, Internet Explorer 7, and Internet Explorer 8 running on supported editions of Windows Server 2003; and Moderate for Internet Explorer 7 and Internet Explorer 8 running on supported editions of Windows Server 2008. For more information, see the subsection, Affected and Non-Affected Software, in this section.

The security update addresses these vulnerabilities by modifying the way that Internet Explorer handles objects in memory and table operations. For more information about the vulnerabilities, see the Frequently Asked Questions (FAQ) subsection under the next section, Vulnerability Information.

Recommendation. The majority of customers have automatic updating enabled and will not need to take any action because this security update will be downloaded and installed automatically. Customers who have not enabled automatic updating need to check for updates and install this update manually. For information about specific configuration options in automatic updating, see Microsoft Knowledge Base Article 294871.

For administrators and enterprise installations, or end users who want to install this security update manually, Microsoft recommends that customers apply the update immediately using update management software, or by checking for updates using the Microsoft Update service.

See also the section, Detection and Deployment Tools and Guidance, later in this bulletin.

Known Issues. None
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Affected and Non-Affected Software

The software listed here have been tested to determine which versions or editions are affected. Other versions or editions are either past their support life cycle or are not affected. To determine the support life cycle for your software version or edition, visit Microsoft Support Lifecycle.

Affected Software
Operating System Component Maximum Security Impact Aggregate Severity Rating Bulletins Replaced by This Update
Internet Explorer 5.01 and Internet Explorer 6 Service Pack 1

Microsoft Windows 2000 Service Pack 4

Microsoft Internet Explorer 5.01 Service Pack 4

Remote Code Execution

Critical

MS09-019

Microsoft Windows 2000 Service Pack 4

Microsoft Internet Explorer 6 Service Pack 1

Remote Code Execution

Critical

MS09-019
Internet Explorer 6

Windows XP Service Pack 2 and Windows XP Service Pack 3

Microsoft Internet Explorer 6

Remote Code Execution

Critical

MS09-019

Windows XP Professional x64 Edition Service Pack 2

Microsoft Internet Explorer 6

Remote Code Execution

Critical

MS09-019

Windows Server 2003 Service Pack 2

Microsoft Internet Explorer 6

Remote Code Execution

Moderate

MS09-019

Windows Server 2003 x64 Edition Service Pack 2

Microsoft Internet Explorer 6

Remote Code Execution

Moderate

MS09-019

Windows Server 2003 with SP2 for Itanium-based Systems

Microsoft Internet Explorer 6

Remote Code Execution

Moderate

MS09-019
Internet Explorer 7

Windows XP Service Pack 2 and Windows XP Service Pack 3

Windows Internet Explorer 7

Remote Code Execution

Critical

MS09-019

Windows XP Professional x64 Edition Service Pack 2

Windows Internet Explorer 7

Remote Code Execution

Critical

MS09-019

Windows Server 2003 Service Pack 2

Windows Internet Explorer 7

Remote Code Execution

Moderate

MS09-019

Windows Server 2003 x64 Edition Service Pack 2

Windows Internet Explorer 7

Remote Code Execution

Moderate

MS09-019

Windows Server 2003 with SP2 for Itanium-based Systems

Windows Internet Explorer 7

Remote Code Execution

Moderate

MS09-019

Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

Windows Internet Explorer 7

Remote Code Execution

Critical

MS09-019

Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

Windows Internet Explorer 7

Remote Code Execution

Critical

MS09-019

Windows Server 2008 for 32-bit Systems* and Windows Server 2008 for 32-bit Systems Service Pack 2*

Windows Internet Explorer 7

Remote Code Execution

Moderate

MS09-019

Windows Server 2008 for x64-based Systems* and Windows Server 2008 for x64-based Systems Service Pack 2*

Windows Internet Explorer 7

Remote Code Execution

Moderate

MS09-019

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

Windows Internet Explorer 7

Remote Code Execution

Moderate

MS09-019
Internet Explorer 8

Windows XP Service Pack 2 and Windows XP Service Pack 3

Windows Internet Explorer 8

Remote Code Execution

Critical

MS09-019

Windows XP Professional x64 Edition Service Pack 2

Windows Internet Explorer 8

Remote Code Execution

Critical

MS09-019

Windows Server 2003 Service Pack 2

Windows Internet Explorer 8

Remote Code Execution

Moderate

MS09-019

Windows Server 2003 x64 Edition Service Pack 2

Windows Internet Explorer 8

Remote Code Execution

Moderate

MS09-019

Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

Windows Internet Explorer 8

Remote Code Execution

Critical

MS09-019

Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

Windows Internet Explorer 8

Remote Code Execution

Critical

MS09-019

Windows Server 2008 for 32-bit Systems* and Windows Server 2008 for 32-bit Systems Service Pack 2*

Windows Internet Explorer 8

Remote Code Execution

Moderate

MS09-019

Windows Server 2008 for x64-based Systems* and Windows Server 2008 for x64-based Systems Service Pack 2*

Windows Internet Explorer 8

Remote Code Execution

Moderate

MS09-019

Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

Windows Internet Explorer 8

Remote Code Execution

Moderate

None

*Windows Server 2008 Server Core installation not affected. The vulnerabilities addressed by this update do not affect supported editions of Windows Server 2008 if Windows Server 2008 was installed using the Server Core installation option. For more information on this installation option, see Server Core. Note that the Server Core installation option does not apply to certain editions of Windows Server 2008; see Compare Server Core Installation Options.

Non-Affected Software
Operating System Component
Internet Explorer 8

Windows 7 for 32-bit Systems

Windows Internet Explorer 8

Windows 7 for x64-based Systems

Windows Internet Explorer 8

Windows 7 for Itanium-based Systems

Windows Internet Explorer 8
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Frequently Asked Questions (FAQ) Related to This Security Update

Why was this security update released out of band?
This security update is being released out of band to address issues disclosed in Microsoft Security Advisory (973882), "Vulnerabilities in Microsoft Active Template Library (ATL) Could Allow Remote Code Execution."

Is this security bulletin related to MS09-035, that is also being released out-of-band?
Yes. Microsoft Security Bulletin MS09-035 describes vulnerabilities in those components and controls that have been developed using vulnerable public versions of the Active Template Library (ATL). As a defense-in-depth measure, this security update (MS09-034) helps mitigate known attack vectors within Internet Explorer for those components and controls that have been developed with the versions of ATL described in Microsoft Security Advisory (973882) and MS09-035.

Is this security bulletin related to Microsoft Security Advisory 973882?
Yes. Microsoft Security Advisory (973882) describes vulnerabilities in public and private versions of the Active Template Library (ATL). As a defense-in-depth measure, this security update (MS09-034) mitigates known attack vectors within Internet Explorer for those components and controls that have been developed with the versions of ATL described in Microsoft Security Advisory (973882) and MS09-035.

Where can I find more information about the Microsoft Active Template Library security vulnerabilities and associated updates?
For more information regarding the Active Template Library (ATL) security vulnerabilities, see Microsoft Security Advisory (973882).

To download the update for ATL, see Microsoft Security Bulletin MS09-035.

If I have installed the MS09-035 update, do I still need to install this update?
Yes. MS09-035 is specifically intended for developers using the Active Template Library (ATL) with Microsoft Visual Studio. Developers who redistribute components and controls built with ATL should install the update provided in MS09-035 to ensure that their components and controls do not contain the vulnerabilities described in that bulletin.

Does this update contain any security-related changes to functionality?
Yes. As a defense-in-depth measure, this Internet Explorer security update helps mitigate known attack vectors within Internet Explorer for those components and controls that have been developed with vulnerable versions of ATL.

In addition to the changes that are listed in the Vulnerability Information section of this bulletin, this update includes two defense-in-depth changes. As such, this update includes a mitigation that helps prevent components and controls built using vulnerable versions of ATL from being exploited in Internet Explorer. The new defense-in-depth protections offered in MS09-034 include updates to Internet Explorer 5.01, Internet Explorer 6 and Internet Explorer 6 Service Pack 1, Internet Explorer 7, and Internet Explorer 8 that monitor and help prevent the successful exploitation of all known public and private library ATL vulnerabilities, including the vulnerabilities that could lead to bypassing ActiveX's kill bit security feature. These protections are designed to help protect customers from Web-based attacks.

The first defense-in-depth measure is enabled by default and modifies how ATL-based ActiveX controls read persisted data. The first mitigation is a change to modify how ATL-based controls read persisted data by detecting specific call patterns that are problematic. One such example is the call pattern that led to the MSVidCtl.dll exploit addressed by MS09-032, one of the security updates released on July 14th. The mitigation addresses the ATL vulnerabilities described in Microsoft Security Advisory (973882) and MS09-035. The change is enabled by default for all affected platforms and will help block ATL vulnerabilities for controls loaded in Internet Explorer, including those not created by Microsoft.

The second defense-in-depth measure is related to the first, but provides stronger protections and increases application compatibility risk. This defense-in-depth measure is disabled by default and offers the ability to regulate usage of IPersistStream* and IPersistStorage* interface implementations within individual controls. Application developers and end-users can opt-in to enable this mitigation for any application using the WebOC using the new Feature Control Key, FEATURE_RESTRICT_OBJECT_DATA_ATTRIBUTE:

Open HKLM or HKCU\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl key in the registry.

Create a subkey for FEATURE_RESTRICT_OBJECT_DATA_ATTRIBUTE, if it doesn't already exist.

Add a new REG_DWORD value for a process name, or * to opt-in all processes, and set its value to 1.

As an example, the following registry value opts in to the Feature Control key, FEATURE_RESTRICT_OBJECT_DATA_ATTRIBUTE for all processes.

HKEY_LOCAL_MACHINE (or HKEY_CURRENT_USER)
SOFTWARE
Microsoft
Internet Explorer
Main
FeatureControl
FEATURE_RESTRICT_OBJECT_DATA_ATTRIBUTE
* = 0x00000001

Individual controls can opt-out of the mitigation by using a new ActiveX Compatibility Flag DWORD value:

HKEY_LOCAL_MACHINE
SOFTWARE
Microsoft
Internet Explorer
ActiveX Compatibility
{CLSID of ActiveX control}
Compatibility Flags = 0x02000000

The FEATURE_RESTRICT_OBJECT_DATA_ATTRIBUTE is currently off by default due to some applications known to load data into IPersistStream* or IPersistStorage* implementations, by design.

Additional Defense in Depth Mitigations and Workaround Guidance for Potentially Vulnerable Controls and Components Built Using Vulnerable Versions of the Active Template Library

By default, the majority of ActiveX controls are not included in the default allow-list for ActiveX controls in Internet Explorer 7 or Internet Explorer 8. Only customers who have explicitly approved vulnerable controls by using the ActiveX opt-in feature are at risk to attempts to exploit this vulnerability. However, if a customer has used such ActiveX controls in a previous version of Internet Explorer, and then later upgraded to Internet Explorer 7 or Internet Explorer 8, then these ActiveX controls are enabled to work in Internet Explorer 7 and Internet Explorer 8, even if the customer has not explicitly approved the ActiveX controls using the ActiveX opt-in feature.

Internet Explorer 8 offers enhanced protections by enabling DEP/NX memory protections by default for users on Windows XP Service Pack 3, Windows Vista Service Pack 1 and Windows Vista Service Pack 2, and Windows 7. DEP/NX helps foil attacks by preventing code from running in memory that is marked non-executable. Combined with Address Space Layout Randomization (ASLR), DEP/NX reduces the ability of attackers to successfully exploit certain types of memory-related vulnerabilities.

Internet Explorer 7 and Internet Explorer 8 on Windows Vista and later operating systems run in Protected Mode by default in the Internet security zone. Protected Mode significantly reduces the ability of an attacker to write, alter, or destroy data on the user's machine or to install malicious code. This is accomplished by using the integrity mechanisms of Windows Vista and later, which restrict access to processes, files, and registry keys with higher integrity levels.

For the development of ActiveX Controls, SiteLock prevents ActiveX Controls from being repurposed by malicious sites by automatically querying the host for the URL of the Web page that is hosting the ActiveX control, extracting the protocol scheme and fully qualified domain name from that URL, and comparing it to a list created by the developer at build time to check whether the hosting site should be trusted.

Where are the file information details?
The file information details can be found in the Microsoft Knowledge Base Article 972260.

I am using an older release of the software discussed in this security bulletin. What should I do?
The affected software listed in this bulletin have been tested to determine which releases are affected. Other releases are past their support life cycle. To determine the support life cycle for your software release, visit Microsoft Support Lifecycle.

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

Severity Ratings and Vulnerability Identifiers

The following severity ratings assume the potential maximum impact of the vulnerability. For information regarding the likelihood, within 30 days of this security bulletin's release, of the exploitability of the vulnerability in relation to its severity rating and security impact, please see the Exploitability Index in the July bulletin summary. For more information, see Microsoft Exploitability Index.
Vulnerability Severity Rating and Maximum Security Impact by Affected Software
Affected Software Memory Corruption Vulnerability - CVE-2009-1917 HTML Objects Memory Corruption Vulnerability - CVE-2009-1918 Uninitialized Memory Corruption Vulnerability - CVE-2009-1919 Aggregate Severity Rating
Internet Explorer 5.01 and Internet Explorer 6 Service Pack 1

Internet Explorer 5.01 Service Pack 4 when installed on Microsoft Windows 2000 Service Pack 4

Not applicable

Critical
Remote Code Execution

Critical

Internet Explorer 6 Service Pack 1 when installed on Microsoft Windows 2000 Service Pack 4

Critical
Remote Code Execution

Critical
Internet Explorer 6

Internet Explorer 6 for Windows XP Service Pack 2 and Windows XP Service Pack 3

Critical
Remote Code Execution

Critical

Internet Explorer 6 for Windows XP Professional x64 Edition Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 6 for Windows Server 2003 Service Pack 2

Moderate
Remote Code Execution

Moderate

Internet Explorer 6 for Windows Server 2003 x64 Edition Service Pack 2

Moderate
Remote Code Execution

Moderate

Internet Explorer 6 for Windows Server 2003 with SP2 for Itanium-based Systems

Moderate
Remote Code Execution

Moderate
Internet Explorer 7

Internet Explorer 7 for Windows XP Service Pack 2 and Windows XP Service Pack 3

Critical
Remote Code Execution

Critical

Internet Explorer 7 for Windows XP Professional x64 Edition Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 7 for Windows Server 2003 Service Pack 2

Moderate
Remote Code Execution

Moderate

Internet Explorer 7 for Windows Server 2003 x64 Edition Service Pack 2

Moderate
Remote Code Execution

Moderate

Internet Explorer 7 for Windows Server 2003 with SP2 for Itanium-based Systems

Moderate
Remote Code Execution

Moderate

Internet Explorer 7 in Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 7 in Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 7 in Windows Server 2008 for 32-bit Systems* and Windows Server 2008 for 32-bit Systems Service Pack 2*

Moderate
Remote Code Execution

Moderate

Internet Explorer 7 in Windows Server 2008 for x64-based Systems* and Windows Server 2008 for x64-based Systems Service Pack 2*

Moderate
Remote Code Execution

Moderate

Internet Explorer 7 in Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

Moderate
Remote Code Execution

Moderate
Internet Explorer 8

Internet Explorer 8 for Windows XP Service Pack 2 and Windows XP Service Pack 3

Critical
Remote Code Execution

Critical

Internet Explorer 8 for Windows XP Professional x64 Edition Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 8 for Windows Server 2003 Service Pack 2

Moderate
Remote Code Execution

Moderate

Internet Explorer 8 for Windows Server 2003 x64 Edition Service Pack 2

Moderate
Remote Code Execution

Moderate

Internet Explorer 8 in Windows Vista, Windows Vista Service Pack 1, and Windows Vista Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 8 in Windows Vista x64 Edition, Windows Vista x64 Edition Service Pack 1, and Windows Vista x64 Edition Service Pack 2

Critical
Remote Code Execution

Critical

Internet Explorer 8 in Windows Server 2008 for 32-bit Systems* and Windows Server 2008 for 32-bit Systems Service Pack 2*

Moderate
Remote Code Execution

Moderate

Internet Explorer 8 in Windows Server 2008 for x64-based Systems* and Windows Server 2008 for x64-based Systems Service Pack 2*

Moderate
Remote Code Execution

Moderate

Internet Explorer 8 in Windows Server 2008 for Itanium-based Systems and Windows Server 2008 for Itanium-based Systems Service Pack 2

Moderate
Remote Code Execution

Moderate

Memory Corruption Vulnerability - CVE-2009-1917

A remote code execution vulnerability exists in the way that Internet Explorer handles a memory object. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-1917.

Mitigating Factors for Memory Corruption Vulnerability - CVE-2009-1917

Mitigation refers to a setting, common configuration, or general best-practice, existing in a default state, that could reduce the severity of exploitation of a vulnerability. The following mitigating factors may be helpful in your situation:
•

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 mitigate attacks that could try to exploit this vulnerability by preventing Active Scripting and ActiveX controls 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 exploitation of this vulnerability through the Web-based attack scenario.
•

By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 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 you have not added to the Internet Explorer Trusted sites zone. See the FAQ subsection of this vulnerability section for more information about Internet Explorer Enhanced Security Configuration.
•

Internet Explorer 5.01 Service Pack 4 when installed on Microsoft Windows 2000 Service Pack 4 is not affected by this vulnerability.
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Workarounds for Memory Corruption Vulnerability - CVE-2009-1917

Workaround refers to a setting or configuration change that does not correct the underlying vulnerability but would help block known attack vectors before you apply the update. Microsoft has tested the following workarounds and states in the discussion whether a workaround reduces functionality:
•

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 exploitation of 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 Internet Explorer, follow these steps:

On the Internet Explorer Tools menu, click Internet Options.

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

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.

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".

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:

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

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

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.

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

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

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 system. Two in particular that you may want to add are *.windowsupdate.microsoft.com and *.update.microsoft.com. These are the sites that will host the update, and it requires an ActiveX Control to install the update.
•

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 exploitation of 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:

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

Click the Security tab.

Click Internet, and then click Custom Level.

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

Click Local intranet, and then click Custom Level.

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

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.

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".

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

To do this, follow these steps:

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

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

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.

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

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

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

FAQ for Memory Corruption Vulnerability - CVE-2009-1917

What is the scope of the vulnerability?
This is a remote code execution vulnerability. An attacker who successfully exploited this vulnerability could gain 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.

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

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could gain the same user rights as a logged-on user. If the user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full 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. The attacker could also take advantage of compromised Web sites and Web sites that accept or host user-provided content or advertisements. 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 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 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 or Windows Server 2008. Does this mitigate this vulnerability?
Yes. By default, Internet Explorer on Windows Server 2003 and Windows Server 2008 runs in a restricted mode that is known as Enhanced Security Configuration. Enhanced Security Configuration is a group of preconfigured settings in Internet Explorer that can reduce the likelihood of a user or administrator downloading and running specially crafted Web content on a server. This is a mitigating factor for Web sites that you have not added to the Internet Explorer Trusted sites zone. See also Managing Internet Explorer Enhanced Security Configuration.

What does the update do?
The update modifies the way that Internet Explorer handles objects in memory.

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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HTML Objects Memory Corruption Vulnerability - CVE-2009-1918

A remote code execution vulnerability exists in the way that Internet Explorer handles table operations in specific situations. An attacker could exploit the vulnerability by constructing a specially crafted Web page. When a user views the Web page, the vulnerability could allow remote code execution. An attacker who successfully exploited this vulnerability could gain the same user rights as the logged-on user. If a user is logged on with administrative user rights, an attacker who successfully exploited this vulnerability could take complete control of an affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

To view this vulnerability as a standard entry in the Common Vulnerabilities and Exposures list, see CVE-2009-1918.

Mitigating Factors for HTML Objects Memory Corruption Vulnerability - CVE-2009-1918

Workarounds for HTML Objects Memory Corruption Vulnerability - CVE-2009-1918