simplestguest.cgi CGI program by Leif Wright allows remote attackers to execute arbitrary commands via shell metacharacters in the guestbook parameter.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5743
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-0022
http://www.securityfocus.com/bid/2106
http://archives.neohapsis.com/archives/bugtraq/2000-12/0168.html