Title: Invalid RDP Data can Cause Terminal Service Failure
Date: 18 October 2001
Software: Windows NT 4.0 Server, Terminal Server Edition,
Windows 2000 Server and Advanced Server
Impact: Denial of service
Max Risk: Moderate
Bulletin: MS01-052

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-052.asp.

Issue:

The implementation of the Remote Data Protocol (RDP) in the terminal
service in Windows NT 4.0 and Windows 2000 does not correctly handle
a particular series of data packets. If such a series of packets
were received by an affected server, it would cause the server to
fail. The server could be put back into normal service by rebooting
it, but any work in progress at the time of the attack would be
lost.

It would not be necessary for an attacker to be able to start a
session with an affected server in order to exploit this
vulnerability - the only prerequisite would be the need to be able
to send the correct series of packets to the RDP port on the server.

Mitigating Factors:

• There is no capability to breach the security of a terminal
  server session via this vulnerability, or to add, change or
  delete data on the server. It is a denial of service
  vulnerability only.
• The specific sequence of data packets involved in this
  vulnerability cannot be generated as part of a legitimate
  terminal server session.

Risk Rating:

• Internet systems: Low
• Intranet systems: Moderate
• Client systems: None

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletin at
  http://www.microsoft.com/technet/security/bulletin/ms01-052.asp
  for information on obtaining this patch.

Acknowledgment:

• Luciano Martins of Deloitte & Touche Argentina
  (http://www.deloitte.com.ar)