Alert: Microsoft Security Bulletin - MS02-024

From: Russ (Russ.Cooper@RC.ON.CA)
Date: 05/23/02

Date:         Thu, 23 May 2002 10:26:26 -0400
From: Russ <Russ.Cooper@RC.ON.CA>

Authentication Flaw in Windows Debugger can Lead to Elevated Privileges (Q320206)

Originally posted: May 22, 2002


Who should read this bulletin: Administrators of Microsoft® Windows NT® 4.0, Windows® 2000 systems.

Impact of vulnerability: Elevation of Privilege

Maximum Severity Rating: Critical

Recommendation: System Administrators should apply the patch to all systems that allow unprivileged users to log onto them interactively.

Affected Software:
- Microsoft Windows NT 4.0
- Microsoft Windows NT 4.0 Server, Terminal Server Edition
- Microsoft Windows 2000

Technical description:

The Windows debugging facility provides a means for programs to perform diagnostic and analytic functions on applications as they are running on the operating system. One of these capabilities allows for a program, usually a debugger, to connect to any running program, and to take control of it. The program can then issue commands to the controlled program, including the ability to start other programs. These commands would then execute in the same security context as the controlled program.

There is a flaw in the authentication mechanism for the debugging facility such that an unauthorized program can gain access to the debugger. A vulnerability results because an attacker can use this to cause a running program to run a program of her choice. Because many programs run as the operating system, this means that an attacker can exploit this vulnerability to run code as the operating system itself. She could take any action on the system including deleting data, adding accounts with administrative access, or reconfiguring the system.

A successful attack requires the ability to logon interactively to the system, either at the console or through a terminal session. Also, an a successful attack requires the introduction of code to exploit this vulnerability. Because best practices recommends restricting the ability to logon interactively on servers, this issue most directly affects client systems and terminal servers.

Mitigating factors:
- A successful attack requires the ability to logon interactively to the target machine, either directly at the console or through a terminal session. Best practices strongly militate against ever allowing an unprivileged user to interactively log onto business-critical systems such as ERP servers, database servers, domain controllers and the like. If these recommendations have been followed, the vulnerability would principally pose a threat only to systems like workstations and terminal servers.
- A successful attack requires that the attacker be able to load code of her choice on the system. Restrictions on a user's ability to load and execute arbitrary code could potentially prevent a successful attack.

Vulnerability identifier: CAN-2002-0367

This email is sent to NTBugtraq automatically as a service to my subscribers. Since its programmatically created, and since its been a long time since anyone paid actual money for my programming skills, it may or may not look that good...;-]

I can only hope that the information it does contain can be read well enough to serve its purpose.

Russ - Surgeon General of TruSecure Corporation/NTBugtraq Editor