MySQL 5.1.x before 5.1.63 and 5.5.x before 5.5.24 allows remote authenticated users to cause a denial of service (mysqld crash) via vectors related to incorrect calculation and a sort order index.

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.

Unspecified vulnerability in the MySQL Server component in Oracle MySQL 5.1.x and 5.5.x allows remote attackers to affect availability via unknown vectors.