Microsoft Security Bulletin MS07-020 Vulnerability in Microsoft Agent Could Allow Remote Code Execution (932168)

Microsoft Security Bulletin MS07-020
Vulnerability in Microsoft Agent Could Allow Remote Code Execution (932168)
Published: April 10, 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: None

Caveats: None

Tested Software and Security Update Download Locations:

Affected Software:
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Microsoft Windows 2000 Service Pack 4 — Download the update
•

Microsoft Windows XP Service Pack 2 — Download the update
•

Microsoft Windows XP Professional x64 Edition and Microsoft Windows XP Professional x64 Edition Service Pack 2 — Download the update
•

Microsoft Windows Server 2003 and Microsoft Windows Server 2003 Service Pack 1 and Microsoft Server 2003 Service Pack 2 — Download the update
•

Microsoft Windows Server 2003 x64 Edition with Service Pack 1 and Microsoft Windows Server 2003 x64 Edition with Service Pack 2 — Download the update
•

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

Non-Affected Software:
•

Windows Vista
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Windows Vista x64 Edition

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 a newly discovered, privately reported vulnerability. The vulnerability is documented in its own subsection in the Vulnerability Details section of this bulletin.

We recommend that customers apply the update immediately.

Severity Ratings and Vulnerability Identifiers:
Vulnerability Identifiers Impact of Vulnerability Microsoft Windows 2000 Service Pack 4 Microsoft Windows XP Service Pack 2 Microsoft Windows Server 2003 Microsoft Windows Server 2003 Service Pack 1 Microsoft Windows Server 2003 Service Pack 2

Microsoft Agent URL Parsing Vulnerability - CVE-2007-1205

Remote Code Execution

Critical

Critical

Moderate

Moderate

Moderate

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 Windows XP Professional x64 Edition and Windows XP Professional x64 Edition Service Pack 2 severity ratings are the same as the Windows Server 2003 Service Pack 1 severity rating.
•

The Windows Server 2003 for Itanium-based Systems severity rating is the same as the Windows Server 2003 severity rating.
•

The Windows Server 2003 with SP2 for Itanium-based Systems severity rating is the same as the Windows Server 2003 Service Pack 2 severity rating.
•

The Windows Server 2003 x64 Edition with Service Pack 1 and Microsoft Windows Server 2003 x64 Edition with Service Pack 2 severity ratings are the same as the Windows Server 2003 Service Pack 2 severity rating.
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Frequently Asked Questions (FAQ) Related to This Security Update

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

Yes

Yes

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

No

Yes

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

No

Yes

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

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

Yes

Yes

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

No

Yes

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

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

Microsoft Agent URL Parsing Vulnerability Could Allow Remote Code Execution- CVE-2007-1205:

A remote code execution vulnerability exists in Microsoft Agent in the way that it handles certain specially crafted URLs.

Mitigating Factors for Microsoft Agent URL Parsing Vulnerability - CVE-2007-1205:
•

In a Web-based attack scenario, an attacker would have to host a Web site that contains a Web page that is used to exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them 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 attacks that could try to 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.
•

Internet Explorer 7 contains code changes that help prevent attempts to exploit this vulnerability. While the vulnerability in Microsoft Agent exists on supported versions of the Windows platforms, Internet Explorer 7 blocks the attack vector into the vulnerability when installed on supported platforms.
•

Windows Vista is not affected by this vulnerability.
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Workarounds for Microsoft Agent URL Parsing Vulnerability - CVE-2007-1205:

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.
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Temporarily prevent the Agent ActiveX control from running in Internet Explorer.

You can help prevent attempts to instantiate this ActiveX control 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 the 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.

To set the kill bit for a CLSID with a value of {D45FD31B-5C6E-11D1-9EC1-00C04FD7081F}, 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\{D45FD31B-5C6E-11D1-9EC1-00C04FD7081F}]

"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{F5BE8BD2-7DE6-11D0-91FE-00C04FD701A5}]

"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{4BAC124B-78C8-11D1-B9A8-00C04FD97575}]

"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{D45FD31D-5C6E-11D1-9EC1-00C04FD7081F}]

"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\ActiveX Compatibility\{D45FD31E-5C6E-11D1-9EC1-00C04FD7081F}]

"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: Web sites that use the Microsoft Agent ActiveX Control will no longer work correctly via Internet Explorer.
•

Unregister AgentSvr.exe

Type the following at a command line or in a logon / machine startup script:

%windir%\msagent\agentsvr.exe /unregserver

Impact of workaround: The Microsoft Agent will no longer work.
•

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:

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

Click Local intranet, and then click Custom Level.

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.

Click OK two times to return to Internet Explorer.

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”.

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 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.
•

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:

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. 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”.

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 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.
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FAQ for Microsoft Agent URL Parsing Vulnerability - CVE-2007-1205:

What is the scope of the vulnerability?
A remote code execution vulnerability exists in Microsoft Agent in the way that it handles certain specially crafted URLs. 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.

What causes the vulnerability?
A specially crafted URL could corrupt system memory in such a way that an attacker could execute arbitrary code when supplied to Microsoft Agent control.

What is Microsoft Agent?
Microsoft Agent is a component that uses interactive animated characters to guide users and can make using and learning to use a computer easier. For more information, see the Microsoft Agent Web site.

What might an attacker use the vulnerability to do?
An attacker who successfully exploited this vulnerability could take complete control of the affected system. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. 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.

Who could exploit the vulnerability?
In a Web-based attack scenario, an attacker would have to host a Web site that contains a Web page that is used to attempt to exploit this vulnerability. An attacker would have no way to force users to visit a specially crafted Web site. Instead, an attacker would have to convince them to visit the Web site, typically by getting them to click a link that takes them to the attacker's site.

What systems are primarily at risk from the vulnerability?
This vulnerability requires 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 this vulnerability.

I am running Windows Internet Explorer 7. Does this mitigate this vulnerability?
Yes. Customers who are running Internet Explorer 7 are not affected by 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 FAQ section of this security update for more information about Internet Explorer Enhanced Security Configuration.

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 Download Center.

What does the update do?
The update removes the vulnerability by making Microsoft Agent gracefully handle specially crafted URL’s.

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:
•

JJ Reyes and Carsten Eiram of Secunia for reporting the Microsoft Agent URL Parsing Vulnerability (CVE-2007-1205).

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:
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V1.0 (April 10, 2007): Bulletin published.