Asterisk Project Security Advisory - AST-2019-003 Product Asterisk Summary Remote Crash Vulnerability in chan_sip channel driver Nature of Advisory Denial of Service Susceptibility Remote Unauthenticated Sessions Severity Minor Exploits Known No Reported On June 28, 2019 Reported By Francesco Castellano Posted On July 1, 2019 Last Updated On July 2, 2019 Advisory Contact Jcolp AT sangoma DOT com CVE Name CVE-2019-13161
Description When T.38 faxing is done in Asterisk a T.38 reinvite may be sent to an endpoint to switch it to T.38. If the endpoint responds with an improperly formatted SDP answer including both a T.38 UDPTL stream and an audio or video stream containing only codecs not allowed on the SIP peer or user a crash will occur. The code incorrectly assumes that there will be at least one common codec when T.38 is also in the SDP answer. This requires Asterisk to initiate a T.38 reinvite which is only done when executing the ReceiveFax dialplan application or performing T.38 passthrough where a remote endpoint has requested T.38. For versions of Asterisk 13 before 13.21.0 and Asterisk 15 before 15.4.0 the âpreferred_codec_onlyâ option must also be set to âyesâ. If set to ânoâ the crash will not occur. Resolution If T.38 faxing is not required this functionality can be disabled by ensuring the ât38pt_udptlâ is set to ânoâ so a T.38 reinvite is not possible. If T.38 faxing is required then Asterisk should be upgraded to a fixed version. The problem can also be limited in scope by enabling T.38 faxing only for endpoints which actually participate in fax. Affected Versions Product Release Series Asterisk Open Source 13.x All releases Asterisk Open Source 15.x All releases Asterisk Open Source 16.x All releases Certified Asterisk 13.21 All releases Corrected In Product Release Asterisk Open Source 13.27.1 Asterisk Open Source 15.7.3 Asterisk Open Source 16.4.1 Certified Asterisk 13.21-cert4 Patches SVN URL Revision http://downloads.asterisk.org/pub/security/AST-2019-003-13.diff Asterisk 13 http://downloads.asterisk.org/pub/security/AST-2019-003-15.diff Asterisk 15 http://downloads.asterisk.org/pub/security/AST-2019-003-16.diff Asterisk 16 http://downloads.asterisk.org/pub/security/AST-2019-003-13.21.diff Certified Asterisk 13.21 Links https://issues.asterisk.org/jira/browse/ASTERISK-28465 Asterisk Project Security Advisories are posted at http://www.asterisk.org/security This document may be superseded by later versions; if so, the latest version will be posted at http://downloads.digium.com/pub/security/AST-2019-003.pdf and http://downloads.digium.com/pub/security/AST-2019-003.html Revision History Date Editor Revisions Made July 1, 2019 Joshua Colp Initial revision Asterisk Project Security Advisory - AST-2019-003 Copyright © 2019 Digium, Inc. All Rights Reserved. Permission is hereby granted to distribute and publish this advisory in its original, unaltered form.
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