IBM DB2 Universal Database (UDB) before 8.1 FixPak 13 allows remote authenticated users to cause a denial of service (crash) by (1) sending the first ACCSEC command without an RDBNAM parameter during the CONNECT process, or (2) sending crafted SQLJRA packet, which results in a null dereference.
http://www.vupen.com/english/advisories/2006/3328
http://www.securityfocus.com/bid/19586
http://www.securityfocus.com/archive/1/454307/100/0/threaded
http://www.securityfocus.com/archive/1/445298/100/0/threaded
http://www.appsecinc.com/resources/alerts/db2/2006-09-05.shtml