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.
MySQL 5.x before 5.0.36 allows local users to cause a denial of service (database crash) by performing information_schema table subselects and using ORDER BY to sort a single-row result, which prevents certain structure elements from being initialized and triggers a NULL dereference in the filesort function.