A vulnerability in the implementation of Session Initiation Protocol (SIP) processing in Cisco Small Business SPA514G IP Phones could allow an unauthenticated, remote attacker to cause an affected device to become unresponsive, resulting in a denial of service (DoS) condition. The vulnerability is due to improper processing of SIP request messages by an affected device. An attacker could exploit this vulnerability by sending crafted SIP messages to an affected device. A successful exploit could allow the attacker to cause the affected device to become unresponsive, resulting in a DoS condition that persists until the device is restarted manually. Cisco has not released software updates that address this vulnerability. This vulnerability affects Cisco Small Business SPA514G IP Phones that are running firmware release 7.6.2SR2 or earlier.