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 base score: 5.3

Status

Package Release Status
asterisk
Launchpad, Ubuntu, Debian
Upstream
Released (1:13.13.1~dfsg-1)
Ubuntu 21.04 (Hirsute Hippo) Not vulnerable
(1:13.13.1~dfsg-1)
Ubuntu 20.10 (Groovy Gorilla) Not vulnerable
(1:13.13.1~dfsg-1)
Ubuntu 20.04 LTS (Focal Fossa) Not vulnerable
(1:13.13.1~dfsg-1)
Ubuntu 18.04 LTS (Bionic Beaver) Not vulnerable
(1:13.13.1~dfsg-1)
Ubuntu 16.04 ESM (Xenial Xerus) Ignored
(end of standard support, was needed)
Ubuntu 14.04 ESM (Trusty Tahr) Does not exist
(trusty was needed)