IBM DB2 9.1 before FP8 does not require the SETSESSIONUSER privilege for the SET SESSION AUTHORIZATION statement, which has unspecified impact and remote attack vectors.
http://www.securityfocus.com/bid/36540
http://www-01.ibm.com/support/docview.wss?uid=swg21403619
http://www-01.ibm.com/support/docview.wss?uid=swg1IZ55883