The Google Authenticator login (ga_login) module 7.x before 7.x-1.3 for Drupal, when multi-factor authentication is enabled, allows remote attackers to bypass authentication for accounts without an associated Google Authenticator token by logging in with the username.
http://www.openwall.com/lists/oss-security/2013/02/05/1
http://drupalcode.org/project/ga_login.git/commitdiff/50b032d