There is a vulnerability in the Internet Explorer java applet handling engine. It occurs while running at Sun Microsystems Java VM and is caused by inproper HTML 'INPUT' control focus handling. After focusing the control before the successful applet intialization numerous browser failures appears. Beside a final DoS condition it causes also a failure in the keyboard and mouse input messages handling in browser (eg: AltF4, browser window close button, document text selection) Sun Microsystems Java need to be installed and set as default VM for IE to exploit this vulnerability. The same Sun Java VM version running at other browsers (eg: Firefox, Opera) works fine and handles this exploitation conditions without any problems, which means it is not the problem with Sun Microsystems Java but with wrong java applet handling implemented in IE. Successful exploitation of this vulnerability causes a DoS condition and a browser crash during to nullpointer assignment in mshtml.dll module in one of IE threads. The example DoS exploit including Java applet source code can be found at: http://www.anspi.pl/~fex/rx6502.html vulnerability found by: porkythepig