sql/item_xmlfunc.cc in MySQL 5.1 before 5.1.32 and 6.0 before 6.0.10 allows remote authenticated users to cause a denial of service (crash) via "an XPath expression employing a scalar expression as a FilterExpr with ExtractValue() or UpdateXML()," which triggers an assertion failure.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A7544
https://exchange.xforce.ibmcloud.com/vulnerabilities/49050
http://www.vupen.com/english/advisories/2009/0594
http://www.securitytracker.com/id?1021786
http://secunia.com/advisories/34115
http://dev.mysql.com/doc/refman/6.0/en/news-6-0-10.html