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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® 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.mspx

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General Information

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

Vulnerability Identifier: CVE-2000-0121

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Patch Availability

•

http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=02DAD2FB-32DE-4003-82CD-BB1831D04898

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

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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.mspx.
•	Microsoft Knowledge Base (KB) article 248399, Shared Workstation Setup may Permit Access to Recycle Bin Files. (A link will be posted here as soon as the article is available, 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/contactussupport/?ws=support.

Acknowledgments

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

Revisions

•	February 1, 2000: Bulletin Created.
•	Thursday, July 13, 2000: Last updated

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