Asterisk SIP Channel Authentication Bypass (AST-2016-009)

Critical Nessus Plugin ID 95927


A telephony application running on the remote host is affected by an authentication bypass vulnerability.


According to its SIP banner, the version of Asterisk running on the remote host is 11.x prior to 11.25.1, 13.x prior to 13.13.1, 14.x prior to 14.2.1, 11.6 prior to 11.6-cert16, or 13.8 prior to 13.8-cert4. Is it, therefore, affected by an authentication bypass vulnerability in the chan_sip channel driver when handling the content between the SIP header name and a colon character due to incorrect stripping of non-printable ASCII characters. An unauthenticated, remote attacker can exploit this issue, via a specially crafted combination of valid and invalid 'To' headers, to cause a proxy to allow an INVITE request into Asterisk without authentication. This is because, in situations where Asterisk is placed in tandem with an authenticating SIP proxy, the proxy will treats the request as an in-dialog request; however, due to this issue, the request will appear to be an out-of-dialog request to Asterisk, which will then be processed as a new call, thus allowing calls from unauthenticated sources.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.


Upgrade to Asterisk version 11.25.1 / 13.13.1 / 14.2.1 / 11.6-cert16 / 13.8-cert4 or later.

See Also

Plugin Details

Severity: Critical

ID: 95927

File Name: asterisk_ast_2016_009.nasl

Version: $Revision: 1.5 $

Type: remote

Family: Misc.

Published: 2016/12/19

Modified: 2017/04/07

Dependencies: 63202

Risk Information

Risk Factor: Critical


Base Score: 10

Temporal Score: 8.3

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C

Temporal Vector: CVSS2#E:F/RL:OF/RC:ND


Base Score: 9.8

Temporal Score: 9

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:F/RL:O/RC:X

Vulnerability Information

CPE: cpe:/a:digium:asterisk

Required KB Items: asterisk/sip_detected, Settings/ParanoidReport

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 2016/12/08

Vulnerability Publication Date: 2016/12/08

Reference Information

CVE: CVE-2016-9938

BID: 94789

OSVDB: 148466