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CVE-2016-9938

Published: 12 December 2016

An issue was discovered in Asterisk Open Source 11.x before 11.25.1, 13.x before 13.13.1, and 14.x before 14.2.1 and Certified Asterisk 11.x before 11.6-cert16 and 13.x before 13.8-cert4. The chan_sip channel driver has a liberal definition for whitespace when attempting to strip the content between a SIP header name and a colon character. Rather than following RFC 3261 and stripping only spaces and horizontal tabs, Asterisk treats any non-printable ASCII character as if it were whitespace. This means that headers such as Contact\x01: will be seen as a valid Contact header. This mostly does not pose a problem until Asterisk is placed in tandem with an authenticating SIP proxy. In such a case, a crafty combination of valid and invalid To headers can cause a proxy to allow an INVITE request into Asterisk without authentication since it believes the request is an in-dialog request. However, because of the bug described above, the request will look like an out-of-dialog request to Asterisk. Asterisk will then process the request as a new call. The result is that Asterisk can process calls from unvetted sources without any authentication. If you do not use a proxy for authentication, then this issue does not affect you. If your proxy is dialog-aware (meaning that the proxy keeps track of what dialogs are currently valid), then this issue does not affect you. If you use chan_pjsip instead of chan_sip, then this issue does not affect you.

Priority

Low

Cvss 3 Severity Score

5.3

Score breakdown

Status

Package Release Status
asterisk
Launchpad, Ubuntu, Debian
jammy Not vulnerable
(1:13.13.1~dfsg-1)
hirsute Not vulnerable
(1:13.13.1~dfsg-1)
xenial Needed

precise Ignored
(end of life)
kinetic Not vulnerable
(1:13.13.1~dfsg-1)
lunar Not vulnerable
(1:13.13.1~dfsg-1)
artful Ignored
(end of life)
bionic Not vulnerable
(1:13.13.1~dfsg-1)
cosmic Not vulnerable
(1:13.13.1~dfsg-1)
disco Not vulnerable
(1:13.13.1~dfsg-1)
eoan Not vulnerable
(1:13.13.1~dfsg-1)
focal Not vulnerable
(1:13.13.1~dfsg-1)
groovy Not vulnerable
(1:13.13.1~dfsg-1)
impish Not vulnerable
(1:13.13.1~dfsg-1)
trusty Does not exist
(trusty was needed)
upstream
Released (1:13.13.1~dfsg-1)
yakkety Ignored
(end of life)
zesty Ignored
(end of life)
mantic Not vulnerable
(1:13.13.1~dfsg-1)

Severity score breakdown

Parameter Value
Base score 5.3
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact Low
Availability impact None
Vector CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N