mysql: possible system table information overwrite using symlinks

MySQL Community Server 5.0.x before 5.0.51, Enterprise Server 5.0.x before 5.0.52, Server 5.1.x before 5.1.23, and Server 6.0.x before 6.0.4, when a table relies on symlinks created through explicit DATA DIRECTORY and INDEX DIRECTORY options, allows remote authenticated users to overwrite system table information and gain privileges via a RENAME TABLE statement that changes the symlink to point to an existing file.