J-057: Windows NT(r) Terminal Servers DOS Vulnerability

PROBLEM:       Microsoft has identified a vulnerability that could cause 
               a denial of service threat using the Terminal Server.
PLATFORM:      Microsoft Windows NT Server 4.0, Terminal Server Edition
DAMAGE:        The vulnerability could allow an attacker to submit a large
               number of bogus connection requests and consume all the 
               memory on the Terminal Server.
SOLUTION:      Apply patches listed below. 
VULNERABILITY  Risk is medium.  This vulnerability could be exploited 
ASSESSMENT:    remotely if connection requests are not filtered.

[  Start Microsoft Advisory  ]

Microsoft Security Bulletin (MS99-028)
--------------------------------------

Patch Available for "Terminal Server Connection Request Flooding"
Vulnerability

Originally Posted: August 09, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability that
could pose a denial-of-service threat to Microsoft(r) Windows NT(r)
Terminal Servers.  Frequently asked questions regarding this vulnerability
can be found at http://www.microsoft.com/security/bulletins/MS99-028faq.asp

Issue
=====
When a request to open a new terminal connection is received by a Terminal
Server, the server undertakes a resource-intensive series of operations to
prepare for the connection. It does this before authenticating the request.
This would allow an attacker to mount a denial of service attack by levying
a large number of bogus connection requests and consuming all memory on the
Terminal Server.

This vulnerability could be exploited remotely if connection requests are
not filtered. In extreme cases, the server could crash in the face of such
an attack; in other cases, normal processing would return when the attack
ceased.  The patch works by causing the server to require authentication
before processing the connection request.

Affected Software Versions
==========================
 - Microsoft Windows NT Server 4.0, Terminal Server Edition

Patch Availability
==================
 - Microsoft Windows NT Server 4.0, Terminal Server Edition:
   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes
   /usa/NT40tse/hotfixes-postSP4/Flood-fix/

   NOTE: Line breaks have been added to the above URL for readability.

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-028: Frequently Asked Questions,
   http://www.microsoft.com/security/bulletins/MS99-028faq.asp.
 - Microsoft Knowledge Base (KB) article Q238600,
   Multiple Connection Requests Promote Denial of Service Attack,
   http://support.microsoft.com/support/kb/articles/q238/6/00.asp.
   (Note: It may take 24 hours from the original posting of this
   bulletin for the KB article to be visible.)
 - Microsoft Security Advisor web site,
   http://www.microsoft.com/security/default.asp.

Obtaining Support on this Issue
===============================
This is a fully supported patch.  Information on contacting Microsoft
Technical Support is available at
http://support.microsoft.com/support/contact/default.asp.

Acknowledgments
===============
Microsoft acknowledges the ISS X-force (http://www.iss.net) for discovering
this vulnerability and working with us to alert customers about it.

Revisions
=========
 - August 09, 1999: Bulletin Created.



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