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Microsoft Security Bulletin (MS00-052)
- --------------------------------------

Patch Available for "Relative Shell Path" Vulnerability

Originally posted: July 28, 2000

Summary
=======
Microsoft has released a patch that eliminates a security
vulnerability in Microsoft(r) Windows NT(r) 4.0 and Windows(r) 2000.
Under certain conditions, the vulnerability could enable a malicious
user to cause code of his choice to run when another user
subsequently logged onto the same machine.

Frequently asked questions regarding this vulnerability
and the patch can be found at
http://www.microsoft.com/technet/security/bulletin/fq00-052.asp

Issue
=====
The registry entry that specifies the Windows Shell executable
(Explorer.exe) provides a relative, rather than absolute, path name.
(As discussed in the FAQ, it does this because of legacy application
compatibility concerns). Because of the circumstances in place at
system startup time, the normal search order would cause any file
named Explorer.exe in the %Systemdrive%\ directory to be loaded in
place of the bona fide version. This could provide an opportunity for
a malicious user to cause code of his choice to run when another user
subsequently logged onto the same machine.

Under normal conditions, the malicious user could only exploit this
vulnerability on machines that he could interactively log onto. As a
result, workstations and terminal servers would be the machines
primarily at risk. If standard security recommendations have been
followed, normal users will not be given permission to interactively
log onto security-critical machines such as domain controllers,
print/file servers, ERP servers, web servers, and so forth.

Affected Software Versions
==========================
 - Microsoft Windows NT 4.0 Workstation
 - Microsoft Windows NT 4.0 Server
 - Microsoft Windows NT 4.0 Server, Enterprise Edition
 - Microsoft Windows NT 4.0 Server, Terminal Server Edition
 - Microsoft Windows 2000 Professional
 - Microsoft Windows 2000 Server
 - Microsoft Windows 2000 Advanced Server

Patch Availability
==================
 - Microsoft Windows NT 4.0 Workstation, Windows NT 4.0 Server,
   and Windows NT 4.0 Server, Enterprise Edition:
   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=23360
 - Microsoft Windows NT 4.0 Server, Terminal Server Edition patches
   will be available soon.
 - Microsoft Windows 2000 Professional, Server, and Advanced Server:
   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=23359

Note: Additional security patches are available at the Microsoft
Download Center

More Information
================
Please see the following references for more information related to
this issue.
 - Frequently Asked Questions: Microsoft Security Bulletin MS00-052,
   http://www.microsoft.com/technet/security/bulletin/fq00-052.asp
 - Microsoft Knowledge Base (KB) article Q269049,
   http://www.microsoft.com/technet/support/kb.asp?ID=269049
 - Microsoft TechNet Security web site,
   http://www.microsoft.com/technet/security/default.asp

Obtaining Support on this Issue
===============================
This is a fully supported patch. Information on contacting Microsoft
Product
Support Services is available at
http://support.microsoft.com/support/contact/default.asp.

Revisions
=========
 - July 28, 2000: Bulletin Created.

- -------------------------------------------------------------

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THE FOREGOING LIMITATION MAY NOT APPLY.

Last Updated July 28, 2000

(c) 2000 Microsoft Corporation. All rights reserved. Terms of use.


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