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Title: Flaw in ISAPI Extension for Windows Media Services
Could Cause Code Execution (817772) Date: 28 May 2003 Software: Microsoft(r) Windows NT(r) 4.0, and Windows(r) 2000 Impact: Allow an attacker to execute code of their choice Max Risk: Important Bulletin: MS03-019
Microsoft encourages customers to review the Security Bulletins at: http://www.microsoft.com/technet/security/bulletin/MS03-019.asp http://www.microsoft.com/security/security_bulletins/ms03-019.asp
On May 28th, Microsoft released the initial version of this bulletin, rating the severity of the vulnerability as Moderate. Subsequent to that release we have determined that the actions an attacker could take as a result of exploiting this vulnerability could include the ability to execute arbitrary code. As a result Microsoft has reissued this bulletin and changed the severity rating to Important. The original corrects the vulnerability and is not being re-released.
Microsoft Windows Media Services is a feature of Microsoft Windows 2000 Server, Advanced Server, and Datacenter Server and is also available as a downloadable version for Windows NT 4.0 Server. Windows Media Services contain support for a method of delivering media content to clients across a network known as multicast streaming. In multicast streaming however, the server has no connection or knowledge of the clients that may be receiving the stream coming from the server. To facilitate logging of client information for the server Windows 2000 includes a capability specifically designed for that purpose. To help with this problem, Windows 2000 includes logging capabilities for multicast and unicast transmissions.
This capability is implemented as an Internet Services Application Programming Interface (ISAPI) extension - nsiislog.dll. When Windows Media Services are installed in Windows NT 4.0 Server or added through add/remove programs to Windows 2000, nsiislog.dll is installed to the Internet Information Services (IIS) Scripts directory on the server.
There is a flaw in the way in which nsiislog.dll processes incoming requests. A vulnerability exists because an attacker could send specially formed communications to the server that could cause IIS to fail or execute code on the user's system.
Windows Media Services is not installed by default on Windows 2000, and must be downloaded to install on Windows NT 4.0. An attacker attempting to exploit this vulnerability would have to be aware which computers on the network had Windows Media Services installed on it and send a specific request to that server.
for information on obtaining this patch.
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