Windows Media Services Unicast Service May Become Unresponsive

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Article ID: 273014 - View products that this article applies to.
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Microsoft has made an update available for the Unicast Service race condition issue. The Microsoft Windows Media Services Unicast Service may become unresponsive and no longer serve content. This vulnerability may allow a malicious user to prevent an affected server from providing useful services.


If a client sends a particular type of malformed request to a Windows Media server, it can induce a race condition. When the server has been put into such a state, subsequent requests, even ones that are usually legitimate can cause the Windows Media Unicast Service to fail. If this happens, any ongoing sessions are lost, and the server stops providing Unicast streaming media services.

You can put an affected server back into service by restarting the Unicast Service. The vulnerability does not cause any data loss, and does not allow the malicious user to usurp any administrative privileges on the computer.


Microsoft has released a patch that eliminates this security vulnerability in Microsoft Windows Media Services.

Frequently asked questions regarding this vulnerability and the patch can be found at the following location:
The following file is available for Microsoft Windows NT Server 4.0 and Microsoft Windows 2000 from the Microsoft Download Center:
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Download Wmsu27678.exe now
The English version of this fix should have the following file attributes or later:
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DateTimeVersionSizeFile NamePlatform
08/23/200012:47:47 PM4.1.0.3920441,312Nsum.exex86 Windows 2000
08/22/200011:01:12 AM4.1.0.3858440,288NSum.exex86 Windows NT


Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article.


Article ID: 273014 - Last Review: February 28, 2014 - Revision: 2.3
  • Microsoft Windows Media Services 4.0
  • Microsoft Windows Media Services 4.1
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