source: http://www.securityfocus.com/bid/2361/info

It is possible for a remote user to gain read access to directories and files outside the root directory of Carey Internet Services Commerce.cgi. Requesting a specially crafted URL composed of '/../%00' along with the known filename or directory will disclose the requested resource. 

http://target/cgi/commerce.cgipage=../../../../etc/hosts%00filename.html