Asterisk Project Security Advisory – AST-2015-003

Product Asterisk
Summary TLS Certificate Common name NULL byte exploit
Nature of Advisory Man in the Middle Attack
Susceptibility Remote Authenticated Sessions
Severity Major
Exploits Known None
Reported On 12 January, 2015
Reported By Maciej Szmigiero
Posted On March 04, 2015
Last Updated On April 8, 2015
Advisory Contact Jonathan Rose
CVE Name CVE-2015-3008

Description When Asterisk registers to a SIP TLS device and and verifies the
server, Asterisk will accept signed certificates that match a
common name other than the one Asterisk is expecting if the
signed certificate has a common name containing a null byte
after the portion of the common name that Asterisk expected. For
example, if Asterisk is trying to register to www.domain.com,
Asterisk will accept certificates of the form
www.domain.com\x00www.someotherdomain.com – for more information
on this exploit, see
https://fotisl.com/blog/2009/10/the-null-certificate-prefix-bug/

Resolution Asterisk has been patched to verify that the common name
length of the certificate matches the common name that
Asterisk actually reads. Asterisk will not accept
certificates with common names that contain null bytes.

Affected Versions
Product Release
Series
Asterisk Open Source 1.8.x All versions
Asterisk Open Source 11.x All versions
Asterisk Open Source 12.x All versions
Asterisk Open Source 13.x All versions
Certified Asterisk 1.8.28 All versions
Certified Asterisk 11.6 All versions
Certified Asterisk 13.1 All versions

Corrected In
Product Release
Asterisk Open Source 1.8.32.3, 11.17.1, 12.8.2 13.3.2
Certified Asterisk 1.8.28-cert5, 11.6-cert11, 13.1-cert2

Patches
SVN URL Revision
http://downloads.asterisk.org/pub/security/AST-2015-003-1.8.28.diff Certified
Asterisk
1.8.28
http://downloads.asterisk.org/pub/security/AST-2015-003-11.6.diff Certified
Asterisk
11.6
http://downloads.asterisk.org/pub/security/AST-2015-003-13.1.diff Certified
Asterisk
13.1
http://downloads.asterisk.org/pub/security/AST-2015-003-1.8.diff Asterisk
1.8
http://downloads.asterisk.org/pub/security/AST-2015-003-11.diff Asterisk
11
http://downloads.asterisk.org/pub/security/AST-2015-003-12.diff Asterisk
12
http://downloads.asterisk.org/pub/security/AST-2015-003-13.diff Asterisk
13

Links https://issues.asterisk.org/jira/browse/ASTERISK-24847

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This document may be superseded by later versions; if so, the latest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-2015-003.pdf and
http://downloads.digium.com/pub/security/AST-2015-003.html

Revision History
Date Editor Revisions Made
19 March, 2015 Jonathan Rose Initial creation of document
08 April, 2015 Matt Jordan Added CVE.

Asterisk Project Security Advisory – AST-2015-003
Copyright (c) 2015 Digium, Inc. All Rights Reserved.
Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.