Asterisk Project Security Advisory – AST-2021-001

Asterisk Project Security Advisory – AST-2021-001

Product Asterisk
Summary Remote crash in res_pjsip_diversion
Nature of Advisory Denial of service
Susceptibility Remote authenticated sessions
Severity Moderate
Exploits Known No
Reported On December 28 2020
Reported By Ivan Poddubny
Posted On January 04 2021
Last Updated On January 04 2021
Advisory Contact gjoseph AT sangoma DOT com
CVE Name CVE-2020-35776

Description If a registered user is tricked into dialing a
malicious number that sends lots of 181 responses to
Asterisk, each one will cause a 181 to be sent back to
the original caller with an increasing number of
entries in the “Supported” header. Eventually the
number of entries in the header exceeds the size of
the entry array and causes a crash.
Modules Affected res_pjsip_diversion.c

Resolution Before updating the “Supported” header with a new entry,
Asterisk now checks that the entry doesn’t already exist and
that adding an entry won’t exceed the size of the entry

Affected Versions
Product Release Series
Asterisk Open Source 13.X 13.38.1
Asterisk Open Source 16.X 16.15.1
Asterisk Open Source 17.X 17.9.1
Asterisk Open Source 18.X 18.1.1

Corrected In
Product Release
Asterisk Open Source 13.38.2, 16.16.1, 17.9.2, 18.2.1

Patch URL Revision 13.38.2 16.16.1 17.9.2 18.2.1


Asterisk Project Security Advisories are posted at

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Revision History
Date Editor Revisions Made
December 29, 2020 George Joseph Initial revision

Asterisk Project Security Advisory – AST-2021-001
Copyright © 2020 Digium, Inc. All Rights Reserved.
Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.