This indicates an attempt to exploit a Memory Corruption vulnerability in the RRAS service of Microsoft Windows.
The vulnerability is a result of a NULL pointer dereference error in the Routing and Remote Access Service (RRAS), which occurs when processing specially crafted requests. A remote attacker can exploit this to crash a vulnerable system, creating a denial of service condition.
Microsoft Windows XP
Microsoft Windows Server 2003
System Compromise: Remote attackers can gain control of vulnerable systems.
Restrict access to UDP ports 135, 137, 138, and 445, and TCP ports 135, 139, 445, and 593.