Mozilla Firefox before 31.0 and Thunderbird before 31.0 allow remote attackers to cause a denial of service (X.509 certificate parsing outage) via a crafted certificate that does not use ASCII character encoding in a required context.
https://bugzilla.mozilla.org/show_bug.cgi?id=997795
http://secunia.com/advisories/60628
https://security.gentoo.org/glsa/201504-01
http://www.mozilla.org/security/announce/2014/mfsa2014-65.html