Jabber Gadu-Gadu Transport (a.k.a. jabber-gg-transport) 2.0.x before 2.0.8 allows remote attackers to cause a denial of service a message with an empty <priority/> tag.
https://exchange.xforce.ibmcloud.com/vulnerabilities/15319
http://www.securityfocus.com/bid/9710
http://www.jabberstudio.org/projects/jabber-gg-transport/releases/view.php?id=429