Microsoft Security Bulletin MS03-019: Flaw in ISAPI Extension for Windows Media Services Could Cause Denial of Service (817772)

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Title:      Flaw in ISAPI Extension for Windows Media Services   
            Could Cause Denial of Service (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:   Moderate
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
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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 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 stop responding to Internet requests.

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. The denial of 
service would only affect IIS, and other services on the server 
would remain unaffected. 

Mitigating Factors:
====================
 - Windows Media Services 4.1 is not installed by default on 
Windows 2000, and must be downloaded to install on Windows NT 4.0.
 - Windows Media Services are not available for Windows 2000 
Professional or Windows NT 4.0 Workstation 
 - The attacker would have to know which server on the network 
Windows Media Services had been installed on.  

Risk Rating:
============
Moderate

Patch Availability:
===================
 - A patch is available to fix this vulnerability. Please read the 
   Security Bulletins at
   
http://www.microsoft.com/technet/security/bulletin/ms03-019.asp
http://www.microsoft.com/security/security_bulletins/ms03-019.asp
   
   for information on obtaining this patch.

Acknowledgment:
===============
 - Brett Moore (brett () softwarecreations co nz)

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