The Cisco IP Phone 7940 allows remote attackers to cause a denial of service (reboot) via a large amount of TCP SYN packets (syn flood) to arbitrary ports, as demonstrated to port 80.
https://www.exploit-db.com/exploits/1411
https://exchange.xforce.ibmcloud.com/vulnerabilities/24117
https://euvd.enisa.europa.eu/vulnerability/EUVD-2006-0187
http://www.vupen.com/english/advisories/2006/0202
http://www.securityfocus.com/bid/16200
http://www.cisco.com/warp/public/707/cisco-response-20060113-ip-phones.shtml
http://securitytracker.com/id?1015488
http://secunia.com/advisories/18479
http://downloads.securityfocus.com/vulnerabilities/exploits/cisco_ip7940_dos.pl