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Flaw in Windows Message Handling through Utility Manager New

A local privilege elevation vulnerability exists in Windows 2000 that could allow a user to gain Local System privileges by sending a specially crafted Windows message to the Utility Manager process.

Issue

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. Utility Manager is an accessibility utility that allows users to check the status of accessibility programs (Microsoft Magnifier, Narrator, On–Screen Keyboard) and to start or stop them.

There is a flaw in the way that Utility Manager handles Windows messages. Windows messages provide a way for interactive processes to react to user events (for example, keystrokes or mouse movements) and communicate with other interactive processes. A security vulnerability results because the control that provides the list of accessibility options to the user does not properly validate Windows messages sent to it. It's possible for one process in the interactive desktop to use a specific Windows message to cause the Utility Manager process to execute a callback function at the address of its choice. Because the Utility Manager process runs at higher privileges than the first process, this would provide the first process with a way of exercising those higher privileges.

By default, the Utility Manager contains controls that run in the interactive desktop with Local System privileges. As a result, an attacker who had the ability to log on to a system interactively could potentially run a program that could send a specially crafted Windows message upon the Utility Manager process, causing it to take any action the attacker specified. This would give the attacker complete control over the system.

The attack cannot be exploited remotely, and the attacker would have to have the ability to interactively log on to the system.

Affected Products

  • Microsoft Windows 2000

Download

Patch: http://microsoft.com/downloads/details.aspx?FamilyId=D415A4AC-E13A-4E8A-BE25-85E7DF686F61&displaylang=en

Further Details

Source: Microsoft Corporation

Reference: Microsoft Corporation

Updated: July 10, 2003

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