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 DoS condition that persists until the device is restarted manually. An attacker could exploit this vulnerability by sending crafted SIP messages to an affected devices. There are no workarounds that address this vulnerability; Cisco has not released and will not release firmware updates to address the vulnerability.”]
Source: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190313-sip