The regular expression parser in TCL before 8.4.17, as used in PostgreSQL 8.2 before 8.2.6, 8.1 before 8.1.11, 8.0 before 8.0.15, and 7.4 before 7.4.19, allows remote authenticated users to cause a denial of service (backend crash) via an out-of-bounds backref number.

The query planner in PostgreSQL before 8.0.11, 8.1 before 8.1.7, and 8.2 before 8.2.2 does not verify that a table is compatible with a "previously made query plan," which allows remote authenticated users to cause a denial of service (server crash) and possibly access database content via an "ALTER COLUMN TYPE" SQL statement, which can be leveraged to read arbitrary memory from the server.