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Microsoft Security Bulletin (MS00-057)

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



Patch Available for "File Permission Canonicalization" Vulnerability



Originally posted: August 10, 2000



Summary

=======

Microsoft has released a patch that eliminates a security

vulnerability in Microsoft(r) Internet Information Server. Under very

restricted conditions, the vulnerability could allow a malicious user

to gain additional permissions to certain types of files hosted on a

web server.



Frequently asked questions regarding this vulnerability and the patch

can be found at

http://www.microsoft.com/technet/security/bulletin/fq00-057.asp



Issue

=====

A canonicalization error can, under certain conditions, cause IIS 4.0

or 5.0 to apply incorrect permissions to certain types of files. If

an affected file residing in a folder with restrictive permissions

were requested via a particular type of malformed URL, the

permissions actually used would be those of a folder in the file's

parentage chain, but not those of the folder the file actually

resides in. If the ancestor folder's permissions were more permissive

than those of the correct folder, the malicious user would gain

additional privileges to the affected file.



The vulnerability is subject to several significant restrictions:

 - It only affects CGI scripts and file types that are implemented

   via ISAPI extensions. It does not affect static web page or

   non-web file types such as .exe, .doc or .bat

 - It only affects servers that expose a web folder structure that

   mirrors the physical folder structure on the server.

 - It does not allow arbitrary permissions to be selected, only

   permissions present on an ancestor folder

 - It provides no way to enumerate the server and locate files that

   could be affected by the vulnerability.



Affected Software Versions

==========================

 - Microsoft Internet Information Server 4.0

 - Microsoft Internet Information Server 5.0



Patch Availability

==================

 - Microsoft Internet Information Server 4.0:

   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=23667

 - Microsoft Internet Information Server 5.0:

   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=23665



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 MS00-057,

   http://www.microsoft.com/technet/security/bulletin/fq00-057.asp

 - Microsoft Knowledge Base article Q269862 discusses this issue and

   will be available soon.

 - 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.



Acknowledgments

===============

Microsoft thanks  Burt Abreu & Søren Skov of VBExplorer.com for

reporting this issue to us and working with us to protect customers.



Revisions

=========

August 10, 2000: Bulletin Created.



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



THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED

"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL

WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF

MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT

SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY

DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,

CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF

MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE

POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION

OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO

THE FOREGOING LIMITATION MAY NOT APPLY.



Last Updated August 10, 2000



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







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