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

[manunkind]

Microsoft Security Bulletin (MS00-090)
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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.

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