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Microsoft Windows Utility Manager Vulnerability
April 13, 2004
Risk Level: High
Summary:
A local elevation of privileges vulnerability exists on the Windows Utility
Manager that allows to any user to take complete control over the operating
system.
Versions Affected:
All products in the Windows 2000 operating system family.
Details:
Microsoft Windows 2000 contains support for Accessibility options within the
operating system. Accessibility support is a series of assistive technologies
within Windows that allow users with disabilities to still be able to access the
functions of the operating system. Accessibility support is enabled or disabled
through shortcuts built into the operating system, or through the Accessibility
Utility Manager. The Utility Manager is an accessibility utility that allows
users to check the status of Accessibility programs (Magnifier, Narrator, On-
Screen Keyboard) and start or stop them. The Utility Manager can be invoked by
pressing Windows Key + U or executing "utilman.exe /start" from the command
line. The Utility Manager Service is enabled by default and runs in the
interactive desktop with Local System privileges.
The Utility Manager has support for context sensitive help. Users can access
this by clicking in the "?" on the title bar and then on an object or by
pressing the F1 key after selecting an object. In order to display the help,
Utility Manager loads winhlp32.exe but does not drop System privileges.
Therefore, winhlp32.exe is executed under the Local System account. While
winhlp32.exe is executing it is possible to send Windows messages to it and
attack it with "Shatter" style attacks.
Winhlp32.exe is executed with its main window hidden but it is very trivial to
make it visible. Once the window is made visible, a typical attack would
involve using the "File Open" dialog to execute a program such as "cmd.exe."
Since the Help window has Local System privileges, the executed program will
have the same privileges.
Further information is available at:
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0908
http://www.microsoft.com/technet/security/bulletin/ms04-011.mspx
To download a demonstration of the exploit, click here.
Fix:
http://www.microsoft.com/downloads/details.aspx?FamilyId=0692C27E-F63A-414C-B3EB-D2342FBB6C00&displaylang=en
Acknowledgement:
Thanks to Cesar Cerrudo and Esteban Martínez Fayó of Application Security, Inc. and to Brett Moore of Security-Assessment.com.
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