CVE 2012-5614
Oracle MySQL 5.1.67 and earlier and 5.5.29 and earlier, and MariaDB 5.5.28a and possibly other versions, allows remote authenticated users to cause a denial of service (mysqld crash) via a SELECT command with an UpdateXML command containing XML with a large number of unique, nested elements.
See the 
CVE page on Mitre.org
for more details.
