source: https://www.securityfocus.com/bid/14182/info

pngren is prone to a remote arbitrary command execution vulnerability.

Reportedly, this issue arises when the user-specified values are passed to the 'kaiseki.cgi' script. Due to this, an attacker can supply arbitrary commands and have them executed in the context of the server.

This issue may facilitate unauthorized remote access in the context of the Web server to the affected computer. 

http://www.example.com/cgi-bin/kaiseki.cgi?file.exetension|command|
http://www.example.com/cgi-bin/kaiseki.cgi?|command|