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Asterisk Project Security Advisory - AST-2018-001

Asterisk Project Security Advisory - AST-2018-001
Posted Feb 21, 2018
Authored by Joshua Colp, Sebastien Duthil | Site asterisk.org

Asterisk Project Security Advisory - The RTP support in Asterisk maintains its own registry of dynamic codecs and desired payload numbers. While an SDP negotiation may result in a codec using a different payload number these desired ones are still stored internally. When an RTP packet was received this registry would be consulted if the payload number was not found in the negotiated SDP. This registry was incorrectly consulted for all packets, even those which are dynamic. If the payload number resulted in a codec of a different type than the RTP stream (for example the payload number resulted in a video codec but the stream carried audio) a crash could occur if no stream of that type had been negotiated. This was due to the code incorrectly assuming that a stream of the type would always exist.

tags | advisory, registry
advisories | CVE-2018-7285
MD5 | c2d13e4e6902f9085785bc357baaa195

Asterisk Project Security Advisory - AST-2018-001

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               Asterisk Project Security Advisory - AST-2018-001

Product Asterisk
Summary Crash when receiving unnegotiated dynamic payload
Nature of Advisory Remote Crash
Susceptibility Remote Unauthenticated Sessions
Severity Major
Exploits Known No
Reported On December 18, 2017
Reported By SA(c)bastien Duthil
Posted On February 21, 2018
Last Updated On February 21, 2018
Advisory Contact Joshua Colp <jcolp AT digium DOT com>
CVE Name CVE-2018-7285

Description The RTP support in Asterisk maintains its own registry of
dynamic codecs and desired payload numbers. While an SDP
negotiation may result in a codec using a different payload
number these desired ones are still stored internally. When
an RTP packet was received this registry would be consulted
if the payload number was not found in the negotiated SDP.
This registry was incorrectly consulted for all packets,
even those which are dynamic. If the payload number
resulted in a codec of a different type than the RTP stream
(for example the payload number resulted in a video codec
but the stream carried audio) a crash could occur if no
stream of that type had been negotiated. This was due to
the code incorrectly assuming that a stream of the type
would always exist.

Resolution The RTP support will now only consult the registry for
payloads which are statically defined. The core has also
been changed to protect against situations where a frame of
media is received for a media type that has not been
negotiated.

To receive these fixes update to the given version of
Asterisk or apply the provided patch. There is no
configuration which can protect against this vulnerability.

Affected Versions
Product Release Series
Asterisk Open Source 13.x Unaffected
Asterisk Open Source 14.x Unaffected
Asterisk Open Source 15.x All versions
Certified Asterisk 13.18 Unaffected

Corrected In
Product Release
Asterisk Open Source 15.2.2

Patches
SVN URL Revision
http://downloads.asterisk.org/pub/security/AST-2018-001-15.diff Asterisk
15

Links https://issues.asterisk.org/jira/browse/ASTERISK-27488

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-2018-001.pdf and
http://downloads.digium.com/pub/security/AST-2018-001.html

Revision History
Date Editor Revisions Made
January 15, 2018 Joshua Colp Initial Revision
February 21, 2018 Joshua Colp Added CVE

Asterisk Project Security Advisory - AST-2018-001
Copyright A(c) 2018 Digium, Inc. All Rights Reserved.
Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.

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