Screen Saver Vulnerability Lets User Privileges Be Elevated

ID: Q221991

The information in this article applies to:

Microsoft Windows NT Server versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4
Microsoft Windows NT Workstation versions 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3, 4.0 SP4
Microsoft Windows NT Server, Enterprise Edition versions 4.0, 4.0 SP4
Microsoft Windows NT Server version 4.0, Terminal Server Edition

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:

http://www.microsoft.com/Windows/ServicePacks/

Q152734 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://www.microsoft.com/support/supportnet/overview/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 this problem could 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

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

Keywords : NT4SP4Fix kbbug4.00 kbfix4.00 nt4sp5fix
Version : winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4
Platform : winnt
Issue type : kbbug