Product

Asterisk

Summary

Re-invite with T.38 and malformed SDP causes crash.

Nature of Advisory

Remote Crash

Susceptibility

Remote Authenticated Sessions

Severity

Minor

Exploits Known

No

Reported On

November 07, 2019

Reported By

Salah Ahmed

Posted On

November 21, 2019

Last Updated On

November 21, 2019

Advisory Contact

bford AT sangoma DOT com

CVE Name

CVE-2019-18976

Description

If Asterisk receives a re-invite initiating T.38 faxing and has a port of 0 and no c line in the SDP, a crash will occur.

Modules Affected

res_pjsip_t38.c

Resolution

If T.38 faxing is not needed, then the “t38_udptl” configuration option in pjsip.conf can be set to “no” to disable the functionality. This option automatically defaults to “no” and would have to be manually turned on to experience this crash.

If T.38 faxing is needed, then Asterisk should be upgraded to a fixed version.

Affected Versions

Product

Release Series

Asterisk Open Source

13.x

All versions

Certified Asterisk

13.21

All versions

Corrected In

Product

Release

Asterisk Open Source

13.29.2

Certified Asterisk

13.21-cert5

Patches

SVN URL

Revision

http://downloads.asterisk.org/pub/security/AST-2019-008-13.diff

Asterisk 13

http://downloads.asterisk.org/pub/security/AST-2019-008-13.21.diff

Certified Asterisk 13.21-cert5

Links

https://issues.asterisk.org/jira/browse/ASTERISK-28612

Asterisk Project Security Advisories are posted at http://www.asterisk.org/security

This document may be superseded by later versions; if so, the latest version will be posted at http://downloads.digium.com/pub/security/.pdf and http://downloads.digium.com/pub/security/.html

Revision History

Date

Editor

Revisions Made

November 12, 2019

Ben Ford

Initial Revision

November 21, 2019

Ben Ford

Added “Posted On” date