Sun Ray Server Software (SRSS) 1.3, when Non-Smartcard Mobility (NSCM) is enabled, allows remote attackers to login as another user by running dtlogin from a system that supports the XDMCP client.
http://www.securityfocus.com/bid/4911
http://www.iss.net/security_center/static/9252.php
http://sunsolve.sun.com/search/document.do?assetkey=1-26-44069-1