Positive Technologies Research Team has discovered a privilege escalation
vulnerability in Windows Message Queuing service (MSMQ).
The IOCTL handler in mqac.sys does not properly validate buffer data
associated with the Irp object, which allows local users to crash the system
or execute arbitrary code with SYSTEM privileges.
Microsoft Windows 2000 Service Pack 4
Windows XP Service Pack 2
Windows Server 2003 Service Pack 2
More info : http://seclists.org/fulldisclosure/2009/Aug/0153.html