Asterisk TLS Certificate Common Name NULL Byte Vulnerability (AST-2015-003)
Medium Nessus Plugin ID 82901
SynopsisA telephony application running on the remote host is affected by a certificate validation vulnerability.
DescriptionAccording to its SIP banner, the version of Asterisk running on the remote host is potentially affected by flaw related to certificate validation when registering a SIP TLS device due to not properly verifying a server hostname against an X.509 Common Name (CN) field that has a NULL byte appended after the expected results. A man-in-the-middle attacker can exploit this, via a crafted certificate, to spoof arbitrary SSL servers and intercept network traffic.
Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.
SolutionUpgrade to Asterisk 126.96.36.199 / 11.17.1 / 12.8.2 / 13.3.2 / 1.8.28-cert5 / 11.6-cert11 / 13.1-cert2, or apply the appropriate patch listed in the Asterisk advisory.