TECHNICAL BULLETIN

T-199: Mozilla Firefox NULL Character CA SSL Certificate Validation Security Bypass Vulnerability

July 31, 2009 15:00 GMT


PROBLEM:	Mozilla Firefox before 3.5 and NSS before 3.12.3 do not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority.
PLATFORM:	Galeon Galeon Browser 1.2.13 Mozilla Browser 1.4 through 1.5 Mozilla Network Security Services (NSS) 3.2 through 3.12.2 Mozilla Firefox 3.0 through 3.0.12
ABSTRACT:	Mozilla Firefox is prone to a security-bypass vulnerability because the application fails to properly validate the domain name in a signed CA certificate, allowing attackers to substitute malicious SSL certificates for trusted ones.

LINKS:
DOE-CIRC BULLETIN:	http://www.doecirc.energy.gov/bulletins/t-199.shtml
OTHER LINKS:	Security Focus http://www.securityfocus.com/bid/35888/discuss AWE http://awe.com/mark/blog/20090730.html Bugzilla https://bugzilla.redhat.com/show_bug.cgi?id=510251 Blackhat https://www.blackhat.com/html/bh-usa-09/bh-usa-09-archives.html#Marlinspike Mozilla http://www.mozilla.com/en-US/ H-Online http://www.h-online.com/security/SSL-flaw-revealed-at-Black-Hat--/news/113880 Wired http://www.wired.com/threatlevel/2009/07/kaminsky/
CVE:	CVE-2009-2408

IMPACT ASSESSMENT:	This risk is HIGH. Widely exploited, High media attention.

Discussion:
Mozilla Firefox is prone to a security-bypass vulnerability because the application fails to properly validate the domain name in a signed CA certificate, allowing attackers to substitute malicious SSL certificates for trusted ones.

Successfully exploiting this issue allows attackers to perform man-in-the-middle attacks or impersonate trusted servers, which will aid in further attacks.
Firefox 3.0 is vulnerable; other versions may also be affected.

Note that additional Mozilla products such as Thunderbird and SeaMonkey may also be affected, but this has not been confirmed.

Recommendation:
Monitor your system for any suspicious activity.

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

DOE-CIRC services are available to DOE, DOE Contractors, and the NIH. DOE-CIRC can be contacted at:

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    E-mail:          doecirc@doecirc.energy.gov
    World Wide Web:  http://www.doecirc.energy.gov

UCRL-MI-119788