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TUCoPS :: Windows Net Apps :: ciacl049.htm

Microsoft "Malformed Request to Domain Controller"



Microsoft "Malformed Request to Domain Controller" Privacy and Legal Notice

CIAC INFORMATION BULLETIN

L-049: Microsoft "Malformed Request to Domain Controller"

February 23, 2001 20:00 GMT
PROBLEM:       A core service running only on Windows 2000 domain
               controllers has a software flaw.  This flaw affects system
               handling of invalid service requests.
PLATFORM:      Windows 2000 Server, Advanced Server and Datacenter Server
DAMAGE:        The sending of invalid service requests to a server
               consumes CPU cycles.  A stream of invalid service requests could
               significantly slow the CPU, resulting in a denial of service
               (DoS) to server resources.
SOLUTION:      Microsoft recommends that all customers apply the patch.

VULNERABILITY The risk is LOW. There are mitigating circumstances, ASSESSMENT: as stated in the Microsoft bulletin.
[******  Begin Microsoft Bulletin  ******]

- ----------------------------------------------------------------------
Title:      Malformed Request to Domain Controller can Cause Denial
            of Service
Date:       20 February 2001
Software:   Windows 2000 Server, Advanced Server and Datacenter
            Server
Impact:     Denial of Service
Bulletin:   MS01-011

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS01-011.asp.
- ----------------------------------------------------------------------

Issue: 
======
A core service running on all Windows 2000 domain controllers (but
not on any other machines) contains a flaw affecting how it processes
a certain type of invalid service request. Specifically, the service
should handle the request at issue here by determining that it is
invalid and simply dropping it; in fact, the service performs some
resource-intensive processing and then sends a response.

If an attacker sent a continuous stream of such requests to an
affected machine, it could consume most or all of the machine's CPU
availability. This could cause the domain controller to process
requests for service slowly or not at all, and could limit the number
of new logons the machine could process and the number of Kerberos
tickets that could be issued.

Mitigating Factors: 
====================
 - The machine would automatically resume normal processing
   as soon as the stream of requests ceased.
 - Although the attacker could, in theory, use the vulnerability
   to completely deny service to network users, in practice the
   attack rarely consumes more than 75% of the available CPU
   resources.
 - Users who were already logged on and were using previously
   issued Kerberos tickets would not be affected by domain
   controller unavailability.
 - If there were multiple domain controllers on the domain, the
   unaffected machines could pick up the other machine's load.
 - If normal security practices have been followed, Internet
   users would be prevented by firewalling and other measures
   from levying requests directly to domain controllers.

Patch Availability: 
===================
 - A patch is available to fix this vulnerability. Please read the
   Security Bulletin
   http://www.microsoft.com/technet/security/bulletin/ms01-011.asp
   for information on obtaining this patch.


- ---------------------------------------------------------------------

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY
DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO
THE FOREGOING LIMITATION MAY NOT APPLY.

[******  End Microsoft Bulletin  ******]



CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin.
CIAC services are available to DOE, DOE Contractors, and the NIH. CIAC can be contacted at:
    Voice:          +1 925-422-8193 (7 x 24)
    FAX:            +1 925-423-8002
    STU-III:        +1 925-423-2604
    E-mail:          ciac@llnl.gov
    World Wide Web:  http://www.ciac.org/
                     http://ciac.llnl.gov
                     (same machine -- either one will work)
    Anonymous FTP:   ftp.ciac.org
                     ciac.llnl.gov
                     (same machine -- either one will work)

This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.
UCRL-MI-119788
[Privacy and Legal Notice]


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