A telephony application running on the remote host is affected by multiple vulnerabilities.
According to its SIP banner, the version of Asterisk running on the remote host is 13.x prior to 13.18.1, 14.x prior to 14.7.1, 15.x prior to 15.1.1, or 13.13 prior to 13.13-cert7. It is therefore, affected by multiple vulnerabilities as described in AST-2017-009, AST-2017-010, and AST-2017-011. Also note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.
Upgrade to Asterisk version 13.18.1 / 14.7.1 / 15.1.1 / 13.13-cert7 or later.