The convert_search_mode_to_innobase function in ha_innodb.cc in the InnoDB engine in MySQL 5.1.23-BK and earlier allows remote authenticated users to cause a denial of service (database crash) via a certain CONTAINS operation on an indexed column, which triggers an assertion error.
MySQL before 4.1.23, 5.0.x before 5.0.42, and 5.1.x before 5.1.18 does not require the DROP privilege for RENAME TABLE statements, which allows remote authenticated users to rename arbitrary tables.