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

Medium Nessus Plugin ID 95927

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VPR Score: 1.4


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: Medium

ID: 95927

File Name: asterisk_ast_2016_009.nasl

Version: 1.8

Type: remote

Family: Misc.

Published: 2016/12/19

Updated: 2019/11/13

Dependencies: 63202

Configuration: Enable paranoid mode

Risk Information

Risk Factor: Medium

VPR Score: 1.4

CVSS Score Source: CVE-2016-9938

CVSS v2.0

Base Score: 5

Temporal Score: 3.7

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

Temporal Vector: CVSS2#E:U/RL:OF/RC:C

CVSS v3.0

Base Score: 5.3

Temporal Score: 4.6

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:digium:asterisk

Required KB Items: asterisk/sip_detected, Settings/ParanoidReport

Exploit Available: false

Exploit Ease: No known exploits are available

Patch Publication Date: 2016/12/08

Vulnerability Publication Date: 2016/12/08

Reference Information

CVE: CVE-2016-9938

BID: 94789