Asterisk Project Security Advisory - AST-2011-001 Product Asterisk Summary Stack buffer overflow in SIP channel driver Nature of Advisory Exploitable Stack Buffer Overflow Susceptibility Remote Authenticated Sessions Severity Moderate Exploits Known No Reported On January 11, 2011 Reported By Matthew Nicholson Posted On January 18, 2011 Last Updated On January 18, 2011 Advisory Contact Matthew Nicholson <mnicholson (at) digium (dot) com [email concealed]> CVE Name Description When forming an outgoing SIP request while in pedantic mode, a stack buffer can be made to overflow if supplied with carefully crafted caller ID information. This vulnerability also affects the URIENCODE dialplan function and in some versions of asterisk, the AGI dialplan application as well. The ast_uri_encode function does not properly respect the size of its output buffer and can write past the end of it when encoding URIs. Resolution The size of the output buffer passed to the ast_uri_encode function is now properly respected. In asterisk versions not containing the fix for this issue, limiting strings originating from remote sources that will be URI encoded to a length of 40 characters will protect against this vulnerability. exten => s,1,Set(CALLERID(num)=${CALLERID(num):0:40}) exten => s,n,Set(CALLERID(name)=${CALLERID(name):0:40}) exten => s,n,Dial(SIP/channel) The CALLERID(num) and CALLERID(name) channel values, and any strings passed to the URIENCODE dialplan function should be limited in this manner. Affected Versions Product Release Series Asterisk Open Source 1.2.x All versions Asterisk Open Source 1.4.x All versions Asterisk Open Source 1.6.x All versions Asterisk Open Source 1.8.x All versions Asterisk Business Edition C.x.x All versions AsteriskNOW 1.5 All versions s800i (Asterisk Appliance) 1.2.x All versions Corrected In Product Release Asterisk Open Source 1.4.38.1, 1.4.39.1, 1.6.1.21, 1.6.2.15.1, 1.6.2.16.1, 1.8.1.2, 1.8.2.1 Asterisk Business Edition C.3.6.2 Patches URL Branch http://downloads.asterisk.org/pub/security/AST-2011-001-1.4.diff 1.4 http://downloads.asterisk.org/pub/security/AST-2011-001-1.6.1.diff 1.6.1 http://downloads.asterisk.org/pub/security/AST-2011-001-1.6.2.diff 1.6.2 http://downloads.asterisk.org/pub/security/AST-2011-001-1.8.diff 1.8 Asterisk Project Security Advisories are posted at http://www.asterisk.org/security This document may be superseded by later versions; if so, the latest version will be posted at http://downloads.digium.com/pub/security/AST-2011-001.pdf and http://downloads.digium.com/pub/security/AST-2011-001.html Revision History Date Editor Revisions Made 2011-01-18 Matthew Nicholson Initial Release Asterisk Project Security Advisory - AST-2011-001 Copyright (c) 2011 Digium, Inc. All Rights Reserved. Permission is hereby granted to distribute and publish this advisory in its original, unaltered form.