Microsoft Security Bulletin (MS00-007)

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Microsoft Security Bulletin (MS00-007)
--------------------------------------

Patch Available for "Recycle Bin Creation" Vulnerability

Originally Posted: February 1, 2000

Summary
=======
Microsoft has released a patch that eliminates a security vulnerability in
Microsoft(r) Windows NT 4.0. Under a very daunting set of conditions, a
malicious user could create, delete or modify files in the Recycle Bin of
another user who shared the machine. In most cases, the vulnerability would
not allow the malicious user to read the files unless they already had read
permission to do so.

Frequently asked questions regarding this vulnerability and
the patch can be found at
http://www.microsoft.com/technet/security/bulletin/fq00-007.asp

Issue
=====
The Windows NT Recycle Bin for a given user maps to a folder, whose name is
based on the owner's SID. The folder is created the first time the user
deletes a file, and the owner is given sole permissions to it. However, if a
malicious user could create the folder before the bona fide one were
created, he or she could assign any desired permissions to it. This would
allow him or her to create, modify or delete files in the Recycle Bin, but
in most cases would not enable them to read files unless he or she already
were able to.

There are several significant limitations that would make it difficult to
exploit this vulnerability:
 - The malicious user would need to create the bogus Recycle
   Bin before the user's bona fide one were created.
 - The malicious user would need to share a machine with the
   other user. The vulnerability would only enable the malicious
   user to take action against the Recycle Bin on the particular
   machine, and the particular partition, that was attacked.
 - The malicious user could add files to the Recycle Bin, but this
   vulnerability would not allow him or her to induce the other
   user to retrieve them.

Affected Software Versions
==========================
 - Microsoft Windows NT Workstation 4.0
 - Microsoft Windows NT Server 4.0
 - Microsoft Windows NT Server 4.0, Enterprise Edition

Patch Availability
==================
 - Intel:
   http://www.microsoft.com/downloads/release.asp?ReleaseID=17606
 - Alpha:
   http://www.microsoft.com/downloads/release.asp?ReleaseID=17607

NOTE: This patch only needs to be applied to Windows NT systems using NTFS
file volumes. The vulnerability is moot for FAT volumes, as FAT provides no
per-user data separation by design. See the FAQ for more information.

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 MS00-007,
   http://www.microsoft.com/technet/security/bulletin/fq00-007.asp.
 - Microsoft Knowledge Base (KB) article Q248399,
   Shared Workstation Setup may Permit Access to Recycle Bin Files.
   (A link will be posted here as soon as the article is available,
   in approximately 24 hours)
 - Microsoft TechNet Security web site.

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

Acknowledgments
===============
Microsoft thanks Arne Vistrom and Nobuo Miwa for reporting this issue to us
and working with us to protect customers.

Revisions
=========
 - February 1, 2000: Bulletin Created.

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