Product

Asterisk

Summary

Remote Crash Vulnerability in audio transcoding

Nature of Advisory

Denial of Service

Susceptibility

Remote Unauthenticated Sessions

Severity

Minor

Exploits Known

No

Reported On

August 7, 2019

Reported By

Gregory Massel

Posted On

Last Updated On

August 26, 2019

Advisory Contact

Jcolp AT sangoma DOT com

CVE Name

CVE-2019-15639

Description

When audio frames are given to the audio transcoding support in Asterisk the number of samples are examined and as part of this a message is output to indicate that no samples are present. A change was done to suppress this message for a particular scenario in which the message was not relevant. This change assumed that information about the origin of a frame will always exist when in reality it may not.

This issue presented itself when an RTP packet containing no audio (and thus no samples) was received. In a particular transcoding scenario this audio frame would get turned into a frame with no origin information. If this new frame was then given to the audio transcoding support a crash would occur as no samples and no origin information would be present. The transcoding scenario requires the “genericplc” option to be set to enabled (the default) and a transcoding path from the source format into signed linear and then from signed linear into another format.

Note that there may be other scenarios that have not been found which can cause an audio frame with no origin to be given to the audio transcoding support and thus cause a crash.

Modules Affected

main/translate.c

Resolution

The “genericplc” option can be disabled in codecs.conf to mitigate the described scenario. It is recommended, however, that Asterisk be upgraded to one of the listed versions or the linked patch applied to protect against potential unknown scenarios.

Affected Versions

Product

Release Series

Asterisk Open Source

13.x

13.28.0

Asterisk Open Source

16.x

16.5.0

Corrected In

Product

Release

Asterisk Open Source

13.28.1

Asterisk Open Source

16.5.1

Patches

SVN URL

Revision

http://downloads.asterisk.org/pub/security/AST-2019-005-13.diff

Asterisk 13

http://downloads.asterisk.org/pub/security/AST-2019-005-16.diff

Asterisk 16

Links

https://issues.asterisk.org/jira/browse/ASTERISK-28499

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This document may be superseded by later versions; if so, the latest version will be posted at http://downloads.digium.com/pub/security/AST-2019-005.pdf and http://downloads.digium.com/pub/security/AST-2019-005.html

Revision History

Date

Editor

Revisions Made

August 26, 2019

Joshua Colp

Initial revision