Alert: Microsoft Security Bulletin - MS03-025
From: Russ (Russ.Cooper_at_RC.ON.CA)
Date: Wed, 9 Jul 2003 13:10:44 -0400 To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM
Flaw in Windows Message Handling through Utility Manager Could Enable Privilege Elevation (822679)
Originally posted: July 9, 2003
Who should read this bulletin: Customers using Microsoft« Windows« 2000
Impact of vulnerability: Privilege elevation
Maximum Severity Rating: Important
Recommendation: Customers should install the patch at the earliest opportunity.
End User Bulletin: An end user version of this bulletin is available at:
- Microsoft Windows 2000
Not Affected Software:
- Microsoft Windows Me
- Microsoft Windows NT Server 4.0
- Microsoft Windows NT Server, Terminal Services Edition
- Microsoft Windows XP
- Microsoft Windows Server 2003
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.
- An attacker would need valid logon credentials to exploit the vulnerability. It could not be exploited remotely.
- Properly secured servers would be at little risk from this vulnerability. Standard best practices recommend only allowing trusted administrators to log on to such systems interactively; without such privileges, an attacker could not exploit the vulnerability.
Vulnerability identifier: CAN-2003-0350
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Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor
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