source: http://www.securityfocus.com/bid/1510/info

If a request containing the null character (%00) is made to the Roxen Web Server, the server will return directory contents, and the source of unparsed scripts and html pages.

For example, a request to
http://www.server.com/%00

Will return the contents of the server's document root directory.

Versions of Roxen WebServer 2.0 prior to 2.0.69 are affected. 

