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Q221991: Screen Saver Vulnerability Lets User Privileges Be Elevated

Article: Q221991
Product(s): Microsoft Windows NT
Version(s): winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4
Operating System(s): 
Keyword(s): kbWinNT400sp4fix kbWinNT400sp5fix
Last Modified: 16-MAY-2002

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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 
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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/

-or-

- 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://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

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

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Keywords          : kbWinNT400sp4fix kbWinNT400sp5fix 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTW400sp4 kbWinNTW400sp3 kbWinNTW400sp2 kbWinNTW400sp1 kbWinNTSsearch kbWinNTSEntSearch kbWinNTSEnt400sp4 kbWinNTSEnt400 kbWinNTS400sp4 kbWinNTS400sp3 kbWinNTS400sp2 kbWinNTS400sp1 kbWinNTS400search kbWinNTS400 kbNTTermServ400 kbNTTermServSearch
Version           : winnt:4.0,4.0 SP1,4.0 SP2,4.0 SP3,4.0 SP4
Hardware          : ALPHA x86
Issue type        : kbbug
Solution Type     : kbfix

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