Microsoft KB Archive/221991

= Screen Saver Vulnerability Lets User Privileges Be Elevated =

Article ID: 221991

Article Last Modified on 9/11/2007

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APPLIES TO


 * Microsoft Windows NT Server 4.0, Terminal Server Edition
 * Microsoft Windows NT Server 4.0 Standard Edition
 * Microsoft Windows NT 4.0 Service Pack 1
 * Microsoft Windows NT 4.0 Service Pack 2
 * Microsoft Windows NT 4.0 Service Pack 3
 * Microsoft Windows NT 4.0 Service Pack 4
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT Server 4.0 Enterprise Edition
 * Microsoft Windows NT 4.0 Service Pack 4

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This article was previously published under Q221991



SYMPTOMS
Windows NT starts a screen saver in the local system context and then immediately changes the context to match that of the logged on user. However, Windows NT does not verify that this change completed successfully. If the change fails, the screen saver is running in a privileged state that permits a specially programmed screen saver to use these privileges to elevate the security of the logged on user.



Windows NT 4.0
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or the individual software update. For information on obtaining the latest service pack, please go to:


 * http://www.microsoft.com/windows/servicepacks/ -or-


 * 152734 how to obtain the latest windows nt 4.0 service pack

For information on obtaining the individual software update, contact Microsoft Product Support Services. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:

http://support.microsoft.com/directory/overview.asp

This hotfix has been posted to the following Internet location as Scrnsavi.exe (x86) and Scrnsava.exe (Alpha):

ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/nt40/hotfixes-postsp4/scrnsav-fix/



STATUS
Microsoft has confirmed that this problem may result in some degree of security vulnerability in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT version 4.0 Service Pack 5.



MORE INFORMATION
For more information on this issue, please see the following Microsoft Security Bulletin at:

http://www.microsoft.com/technet/security/bulletin/MS99-008.mspx

For additional security related information about Microsoft products, visit the Microsoft Security Web site at:

http://www.microsoft.com/security

Additional query words: 4.00 Patch Available for Windows NT "Screen Saver" Vulnerability

Keywords: kbhotfixserver kbqfe kbbug kbfix kbqfe KB221991

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