Asterisk chan_sip Overlap Dialing Feature DoS (AST-2016-007)
Medium Nessus Plugin ID 93534
SynopsisA telephony application running on the remote host is affected by a denial of service vulnerability.
DescriptionAccording to its SIP banner, the version of Asterisk running on the remote host is 11.x prior to 11.23.1, 13.x prior to 13.11.1, 11.6-certx prior to 11.6-cert15, or 13.8-certx prior to 13.8-cert3. It is, therefore, affected by a flaw in the overlap dialing feature in chan_sip due to a failure to release old RTP resources before allocating new ones. An unauthenticated, remote attacker can exploit this to exhaust available RTP ports and stop new RTP sessions from being created, resulting in a denial of service condition. This vulnerability only affects installations using the overlap dialing support feature.
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 version 11.23.1 / 13.11.1 / 11.6-cert15 / 13.8-cert3 or later. Alternatively, disable the overlap dialing support feature.