Vulnerability Note VU#716872

Microsoft Agent fails to properly handle specially crafted URLs

Overview

Microsoft Agent fails to properly handle specially crafted URLs, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable system

I. Description

Microsoft Agent is software that provides animated characters to enhance interaction with computer systems. Microsoft Agent comes with Microsoft Windows systems. Microsoft Agent functionality is exposed as an ActiveX control that can be used by web pages. Microsoft Agent fails to properly handle specially crafted URLs, which can result in memory corruption.

According to public reports, exploit code is availabe for this vulnerability.

II. Impact

By convincing a user to view a specially crafted HTML document (e.g., a web page or an HTML email message or attachment), an attacker may be able to execute arbitrary code with the privileges of the user. The attacker could also cause the web browser to crash.

More information is available in Microsoft Security Bulletin MS07-051.

III. Solution

Apply an update

This issue is addressed in Microsoft Security Bulletin MS07-051.

Disable the Microsoft Agent ActiveX controls in Internet Explorer

The vulnerable ActiveX controls can be disabled in Internet Explorer by setting the kill bit for the following CLSIDs:

{D45FD31B-5C6E-11D1-9EC1-00C04FD7081F}
{F5BE8BD2-7DE6-11D0-91FE-00C04FD701A5}
{4BAC124B-78C8-11D1-B9A8-00C04FD97575}
{D45FD31D-5C6E-11D1-9EC1-00C04FD7081F}
{D45FD31E-5C6E-11D1-9EC1-00C04FD7081F}

More information about how to set the kill bit is available in Microsoft Support Document 240797. Alternatively, the following text can be saved as a .REG file and imported to set the kill bit for this control:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{D45FD31B-5C6E-11D1-9EC1-00C04FD7081F}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{F5BE8BD2-7DE6-11D0-91FE-00C04FD701A5}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{4BAC124B-78C8-11D1-B9A8-00C04FD97575}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{D45FD31D-5C6E-11D1-9EC1-00C04FD7081F}]
"Compatibility Flags"=dword:00000400

[HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerActiveX Compatibility{D45FD31E-5C6E-11D1-9EC1-00C04FD7081F}]
"Compatibility Flags"=dword:00000400

Unregister AgentSvr.exe

The Microsoft Agent ActiveX controls interact with the Microsoft Agent Server (AgentSvr.exe) to provide Agent functionality. The Microsoft Agent Server can be unregistered to mitigate this vulnerability by running the following command:

%windir%msagentagentsvr.exe /unregserver

Disable ActiveX

Disabling ActiveX controls in the Internet Zone (or any zone used by an attacker) appears to prevent exploitation of this and other ActiveX vulnerabilities. Instructions for disabling ActiveX in the Internet Zone can be found in the "Securing Your Web Browser" document.

Systems Affected

Vendor	Status	Date Updated
Microsoft Corporation	Vulnerable	11-Sep-2007

References

http://www.microsoft.com/technet/security/bulletin/ms07-051.mspx
http://secunia.com/advisories/26753/
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=592
http://www.pcworld.com/article/id,137166-c,hackers/article.html

Credit

This vulnerability was publicly disclosed in Microsoft Security Bulletin MS07-051. Microsoft in turn credits the Vulnerability Research team of Assurent Secure Technologies, Yamata Li of Palo Alto Networks, and An anonymous researcher working with VeriSign iDefense VCP.

This document was written by Jeff Gennari.

Other Information

Date Public	09/11/2007
Date First Published	09/11/2007 02:24:53 PM
Date Last Updated	09/14/2007
CERT Advisory
CVE Name	CVE-2007-3040
Metric	0.00
Document Revision	13