A vulnerability in the Session Initiation Protocol (SIP) inspection engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload or trigger high CPU, resulting in a denial of service (DoS) condition.
The vulnerability is due to improper handling of SIP traffic. An attacker could exploit this vulnerability by sending SIP requests designed to specifically trigger this issue at a high rate across an affected device.
Source: https://tools.cisco.com/security/center ... td-sip-dos