This indicates an attack attempt to exploit a Denial of Service vulnerability in Internet Authentication Service or Network Policy Server of Windows Server.
The vulnerability is due to an error when the vulnerable application handles a crafted RADIUS Accept-Request query. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system.
Windows Server 2003
Windows Server 2008
Windows Server 2008 R2
Windows Server 2012
Windows Server 2012 R2
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.