MySQL is a popular multi-threaded, multi-user SQL database server.
The processing of the COM_TABLE_DUMP command by a MySQL server fails to properly validate packets that arrive from the client via a network socket.
By crafting specific malicious packets an attacker could gather confidential information from the memory of a MySQL server process, for example results of queries by other users or applications. By using PHP code injection or similar techniques it would be possible to exploit this flaw through web applications that use MySQL as a database backend.
Note that on 5.x versions it is possible to overwrite the stack and execute arbitrary code with this technique. Users of MySQL 5.x are urged to upgrade to the latest available version.
There is no known workaround at this time.
All MySQL users should upgrade to the latest version.
# emerge --sync
# emerge --ask --oneshot --verbose ">=dev-db/mysql-4.0.27"