TECHNICAL BULLETIN

T-201: Mozilla Firefox and Seamonkey Regular Expression Parsing Heap Buffer Overflow Vulnerability

[CVE-2009-2466]

August 3, 2009 12:00 GMT


PROBLEM:	Mozilla Firefox and Seamonkey are prone to a heap-based buffer-overflow vulnerability in the regular expression parser used to match common names in SSL certificates.
PLATFORM:	Mozilla Firefox 3.0.12 Mozilla SeaMonkey 1.0.8
ABSTRACT:	Moxie Marlinspike reported a heap overflow vulnerability in the code that handles regular expressions in certificate names. This vulnerability could be used to compromise the browser and run arbitrary code by presenting a specially crafted certificate to the client. This code provided compatibility with the non-standard regular expression syntax historically supported by Netscape clients and servers. With version 3.5 Firefox switched to the more limited industry-standard wildcard syntax instead and is not vulnerable to this flaw.

LINKS:
DOE-CIRC BULLETIN:	http://www.doecirc.energy.gov/bulletins/t-201.shtml
OTHER LINKS:	Mozilla http://www.mozilla.org/security/announce/2009/mfsa2009-43.html Security Focus http://www.securityfocus.com/bid/35776/info
CVE:	CVE-2009-2466

IMPACT ASSESSMENT:	This risk is high. Successful exploit could result in complete compromise of machine.

[***** Start CVE-2009-2466 *****]
Discussion:
IOActive security researcher Dan Kaminsky reported a mismatch in the treatment of domain names in SSL certificates between SSL clients and the Certificate Authorities (CA) which issue server certificates. In particular, if a malicious person requested a certificate for a host name with an invalid null character in it most CAs would issue the certificate if the requester owned the domain specified after the null, while most SSL clients (browsers) ignored that part of the name and used the unvalidated part in front of the null. This made it possible for attackers to obtain certificates that would function for any site they wished to target. These certificates could be used to intercept and potentially alter encrypted communication between the client and a server such as sensitive bank account transactions.

Solution:
Vendor patch has been released. This patch release also fixes a number of other serious or critical vulnerabilities in Firefox including the NULL Character CA SSL Certificate Validation Security Bypass Vulnerability reported in DOECIRC bulletin T-199 and CVE-2009-2408. 
[***** End CVE-2009-2466 *****]

DOE-CIRC wishes to acknowledge the contributions of IOActive security researcher Dan Kaminsky and Moxie Marlinspike for the information contained in this bulletin.

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UCRL-MI-119788