Microsoft Security Bulletin (MS00-090)
Patch Available for ".ASX Buffer Overrun" and ".WMS Script Execution"
Originally posted: November 22, 2000
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
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.
- Windows Media Player 6.4:
- Windows Media Player 7:
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
Please see the following references for more information related to
- Frequently Asked Questions: Microsoft Security Bulletin MS00-090,
- Microsoft Knowledge Base article Q280419 discusses this issue
and will be available soon.
- Microsoft TechNet Security web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Product Support Services is available at
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
- GFI (http://gfi.com) for reporting the ".WMS Script Execution"
vulnerability to us and working with us to protect customers.
- November 22, 2000: Bulletin Created.
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