The Cisco Unified IP Phone 7960G and 7940G (SIP) do not correctly parse some malformed RTP headers leading to a deterministic denial of service.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/73908/ciscortp-dos.txt
Source: https://packetstormsecurity.com/files/73908/Cisco-Unified-IP-Phone-7960G-and-7940G-SIP-RTP-Header-Vulnerability.html