httpd.c in httpd in the management GUI in DD-WRT 24 sp1, and other versions before build 12533, allows remote attackers to execute arbitrary commands via shell metacharacters in a request to a cgi-bin/ URI.
http://www.theregister.co.uk/2009/07/21/critical_ddwrt_router_vuln/
http://www.exploit-db.com/exploits/9209