Fedora Commons before 2.2.1 does not properly handle certain authentication requests involving Java Naming and Directory Interface (JNDI), related to (1) a nonexistent account name in combination with an empty password, which allows remote attackers to trigger a certain "unexpected / strange response" from an LDAP server, and (2) a reauthentication attempt that throws an exception, which allows remote attackers to trigger use of a cached authentication decision.  NOTE: authentication can be bypassed by using vector 1 followed by vector 2, and possibly can be bypassed by using a single vector.