MySQL before 5.1.48 allows remote authenticated users with alter database privileges to cause a denial of service (server crash and database loss) via an ALTER DATABASE command with a #mysql50# string followed by a . (dot), .. (dot dot), ../ (dot dot slash) or similar sequence, and an UPGRADE DATA DIRECTORY NAME command, which causes MySQL to move certain directories to the server data directory.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11869
http://www.vupen.com/english/advisories/2010/1918
http://www.ubuntu.com/usn/USN-1397-1
http://www.ubuntu.com/usn/USN-1017-1
http://secunia.com/advisories/40762
http://secunia.com/advisories/40333
http://lists.fedoraproject.org/pipermail/package-announce/2010-July/044546.html