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.