source: http://www.securityfocus.com/bid/5357/info

The Microsoft Windows Media Player executable is prone to a buffer overflow condition when invoked with an oversized filename.

Since the program is executed in the context of the user invoking it, it is not likely that a local attacker could exploit this issue to gain elevated privileges. However, if the program can be invoked remotely or a user can be somehow enticed into invoking the program with a malformed filename, then this may be exploited by an attacker. Realistically, another exposure or vulnerability would have to exist on the host system for an attacker to exploit this issue.

It is not currently known exactly which versions of the software are affected. 

From the command prompt it is possible to reproduce this issue with this command:

mplay32.exe A<x279>.mp3

On an unpatched IIS server it is possibly to invoke the application with the following request:

http://target/scripts/..%255c..%255cwinnt/system32.exe?/A<x279>.mp3