A vulnerability in the Session Initiation Protocol (SIP) call-handling functionality of Cisco IP Phone 6800, 7800, and 8800 Series Phones with Multiplatform Firmware could allow an unauthenticated, remote attacker to cause an affected phone to reload unexpectedly, resulting in a temporary denial of service (DoS) condition. The vulnerability exists because the firmware of an affected phone incorrectly handles errors that could occur when an incoming phone call is not answered. An attacker could exploit this vulnerability by sending a set of maliciously crafted SIP packets to an affected phone. A successful exploit could allow the attacker to cause the affected phone to reload unexpectedly, resulting in a temporary DoS condition. This vulnerability affects Cisco IP Phone 6800, 7800, and 8800 Series Phones with Multiplatform Firmware if they are running a Multiplatform Firmware release prior to Release 11.1(2). Cisco Bug IDs: CSCvi24718.