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Title: Flaw in ISAPI Extension for Windows Media Services Could
Cause Code Execution (822343)
Date: 25 June 2003
Software: Microsoft(r) Windows(r) 2000
Impact: Allow an attacker to execute code of their choice
Max Risk: Important
Bulletin: MS03-022

Microsoft encourages customers to review the Security Bulletins at:
http://www.microsoft.com/technet/security/bulletin/MS03-022.asp
http://www.microsoft.com/security/security_bulletins/ms03-022.asp

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Issue:

Microsoft Windows Media Services is a feature of Microsoft Windows
2000 Server, Advanced Server, and Datacenter Server and is also
available in a downloadable version for Windows NT 4.0 Server.
Windows Media Services contains support for a method of delivering
media content to clients across a network known as multicast
streaming. In multicast streaming, the server has no connection to
or knowledge of the clients that may be receiving the stream of
media content coming from the server. To facilitate logging of
client information for the server, Windows 2000 includes a
capability specifically designed to enable logging for multicast
transmissions.

This logging capability is implemented as an Internet Services
Application Programming Interface (ISAPI) extension - nsiislog.dll.
When Windows Media Services are added through add/remove programs to
Windows 2000, nsiislog.dll is installed in the Internet Information
Services (IIS) Scripts directory on the server. Once Windows Media
Services is installed, nsiislog.dll is automatically loaded and used
by IIS.

There is a flaw in the way nsiislog.dll processes incoming client
requests. A vulnerability exists because an attacker could send
specially formed HTTP request (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.
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.

Mitigating Factors:

• Windows Media Services 4.1 is not installed by default on Windows

• Windows Media Services are not available for Windows 2000
  Professional.

Risk Rating:

Important

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletins at

http://www.microsoft.com/technet/security/bulletin/ms03-022.asp
http://www.microsoft.com/security/security_bulletins/ms03-022.asp

for information on obtaining this patch.

Acknowledgment:

• Brett Moore ([email protected])

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