sql/password.c in Oracle MySQL 5.1.x before 5.1.63, 5.5.x before 5.5.24, and 5.6.x before 5.6.6, and MariaDB 5.1.x before 5.1.62, 5.2.x before 5.2.12, 5.3.x before 5.3.6, and 5.5.x before 5.5.23, when running in certain environments with certain implementations of the memcmp function, allows remote attackers to bypass authentication by repeatedly authenticating with the same incorrect password, which eventually causes a token comparison to succeed due to an improperly-checked return value.
bugs.mysql.com/bug.php?id=64884
kb.askmonty.org/en/mariadb-5162-release-notes/
lists.opensuse.org/opensuse-security-announce/2012-08/msg00007.html
seclists.org/oss-sec/2012/q2/493
secunia.com/advisories/49417
secunia.com/advisories/53372
security.gentoo.org/glsa/glsa-201308-06.xml
securitytracker.com/id?1027143
www.exploit-db.com/exploits/19092
www.securityfocus.com/bid/53911
community.rapid7.com/community/metasploit/blog/2012/06/11/cve-2012-2122-a-tragically-comedic-security-flaw-in-mysql