Screen Saver Vulnerability Lets User Privileges Be Elevated (221991)


The information in this article applies to:

  • Microsoft Windows NT Server 4.0 Terminal Server Edition
  • Microsoft Windows NT Server 4.0
  • Microsoft Windows NT Server 4.0 SP1
  • Microsoft Windows NT Server 4.0 SP2
  • Microsoft Windows NT Server 4.0 SP3
  • Microsoft Windows NT Server 4.0 SP4
  • Microsoft Windows NT Workstation 4.0
  • Microsoft Windows NT Workstation 4.0 SP1
  • Microsoft Windows NT Workstation 4.0 SP2
  • Microsoft Windows NT Workstation 4.0 SP3
  • Microsoft Windows NT Workstation 4.0 SP4
  • Microsoft Windows NT Server, Enterprise Edition 4.0
  • Microsoft Windows NT Server, Enterprise Edition 4.0 SP4
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.

RESOLUTION

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:
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/security/bulletins/MS99-008.asp

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

http://www.microsoft.com/security

Modification Type:MinorLast Reviewed:9/23/2005
Keywords:kbHotfixServer kbQFE kbbug kbfix kbQFE KB221991
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