Heap-based buffer overflow in Oracle MySQL 5.5.19 and other versions through 5.5.28, and MariaDB 5.5.28a and possibly other versions, allows remote authenticated users to cause a denial of service (memory corruption and crash) and possibly execute arbitrary code, as demonstrated using certain variations of the (1) USE, (2) SHOW TABLES, (3) DESCRIBE, (4) SHOW FIELDS FROM, (5) SHOW COLUMNS FROM, (6) SHOW INDEX FROM, (7) CREATE TABLE, (8) DROP TABLE, (9) ALTER TABLE, (10) DELETE FROM, (11) UPDATE, and (12) SET PASSWORD commands.