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Microsoft Security Bulletin (MS00-090)

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



Patch Available for ".ASX Buffer Overrun" and ".WMS Script Execution"

Vulnerabilities



Originally posted: November 22, 2000



Summary

=======

Microsoft has released a patch that eliminates two security

vulnerabilities in Microsoft(r) Windows Media(tm) Player. These

vulnerabilities could potentially enable a malicious user to cause a

program of his choice to run on another user's computer.



Frequently asked questions regarding this vulnerability

and the patch can be found at

http://www.microsoft.com/technet/security/bulletin/fq00-090.asp



Issue

=====

The two vulnerabilities discussed below are unrelated to each other

except by the fact that they both affect Windows Media Player. We

packaged them in a single patch to make it more convenient for

customers to apply. The vulnerabilities are:

 - The ".ASX Buffer Overrun" vulnerability. Windows Media

   Player supports the use of Active Stream Redirector (.ASX)

   files to enable users to play streaming media that resides

   on intranet or Internet sites. However, the code that parses

   .ASX files has an unchecked buffer, and this could potentially

   enable a malicious user to run code of his choice on the

   machine of another user. The malicious user could either send

   an affected file to another user and entice her to run or

   preview it, or he could host such a file on a web site and

   cause it to launch automatically whenever a user visited the

   site. The code could take any action on the machine that the

   legitimate user herself could take.

 - The ".WMS Script Execution" vulnerability. Windows Media

   Player 7 introduced a feature called "skins", that allows

   customization of the look and feel of Windows Media Player.

   However, a custom skin (.WMS) file could potentially include

   script, which would execute if Windows Media Player was run

   and that skin was selected. A malicious user could either send

   a customized skin containing script to another user and try to

   entice her into using it, or he could host such a file on a web

   site and cause it to launch automatically whenever a user

   visited the site. Because the code would reside on the user's

   local machine, it would be able to execute ActiveX controls,

   including ones not marked "safe for scripting". This would

   enable the code to take any action that can be accomplished

   via an ActiveX control.



Affected Software Versions

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

 - Microsoft Windows Media Player 6.4

 - Microsoft Windows Media Player 7



Note: The ".ASX Buffer Overrun" affects Windows Media Player versions

6.4 and 7. The ".WMS Script Execution" affects only Windows Media

Player version 7. The patch installs the correct fix(es) for the

particular version of Windows Media Player in use.



Patch Availability

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

 - Windows Media Player 6.4:

   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=26069

 - Windows Media Player 7:

   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=26067



Note: The fix for this issue also will be available as part of the

next periodic update, scheduled for December 2000.



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 MS00-090,

   http://www.microsoft.com/technet/security/bulletin/fq00-090.asp

 - Microsoft Knowledge Base article Q280419 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  the following people:

 - AtStake (http://www.atstake.com) for reporting the ".ASX

   Buffer Overrun" issue to us and working with us to protect

   customers.

 - GFI (http://gfi.com) for reporting the ".WMS Script Execution"

   vulnerability to us and working with us to protect customers.



Revisions

=========

 - November 22, 2000: Bulletin Created.



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



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