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TUCoPS :: Windows Net Apps :: ciacj049.txt

Windows NT DoS Las Request Csrss Exe





             __________________________________________________________

                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___
             __________________________________________________________

                             INFORMATION BULLETIN
               Windows NT, Two Denial-of-Service Vulnerabilities
          (Malformed LSA Request and CSRSS Worker Thread Exhaustion)


June 23, 1999 17:00 GMT                                           Number J-049
______________________________________________________________________________
PROBLEM:        Two vulnerabilities have been identified by Microsoft in
                Windows NT.
                1) A malformed request to the Local Security Authority (LSA)
                service causes the service to stop responding.
                2) CSRSS.EXE worker thread exhaustion can cause a denial of
                service.
PLATFORM:       Windows NT 4.0, workstation and server.
DAMAGE:         These vulnerabilities could allow denial of service attacks.
SOLUTION:       Apply available patches from Microsoft.

______________________________________________________________________________
VULNERABILITY   Risk is low.  Systems running these services could suffer a
ASSESSMENT:     denial of service but no damage results.  Rebooting the system
                clears the denial of service.

______________________________________________________________________________

[  Start Microsoft Advisory  ]

1) "Malformed LSA Request" Vulnerability

Microsoft Security Bulletin (MS99-020)
- --------------------------------------

Patch Available for "Malformed LSA Request" Vulnerability

Originally Posted: June 23, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability that poses a
denial of service threat to Microsoft(r) Windows NT(r) servers and
workstations. A malformed request to the Local Security Authority (LSA)
service will causes the service to stop responding, requiring the computer
to be restarted.

A fully supported patch is available to eliminate the vulnerability, and
Microsoft recommends that affected customers download and install it, if
appropriate.

Issue
=====
Windows NT provides the ability to manage user privileges programmatically
via the Local Security Authority (LSA) API. The API allows a program to
query user names, modify privileges, and change other elements of the
security policy, subject to the program's authorizations.

Certain API methods do not correctly handle certain types of invalid
arguments. The vulnerability is a denial of service threat only, and
service can be restored by restarting the machine. There is no capability
to use this vulnerability to obtain unauthorized services from LSA.

While there are no reports of customers being adversely affected by this
vulnerability, Microsoft is proactively releasing this patch to allow
customers to take appropriate action to protect themselves against it.

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

What Microsoft is Doing
=======================
Microsoft has released patches that fix the problem identified. The patches
are available for download from the sites listed below in What Customers
Should Do.

Microsoft also has sent this security bulletin to customers
subscribing to the Microsoft Product Security Notification Service.
See http://www.microsoft.com/security/services/bulletin.asp for
more information about this free customer service.

Microsoft has published the following Knowledge Base (KB) article on this
issue:
 - Microsoft Knowledge Base (KB) article Q231457,
   Malformed Request Causes LSA Service to Hang,
   http://support.microsoft.com/support/kb/articles/q231/4/57.asp
   (Note: It might take 24 hours from the original posting of
   this bulletin for the KB article to be visible in the Web-based
   Knowledge Base.)

What Customers Should Do
========================
Microsoft has released patches that fix the problem identified.
Microsoft highly recommends that customers evaluate the degree of
risk that this vulnerability poses to their systems and determine
whether to download and install the patch. The patch can be found at:
 - ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa
   /NT40/hotfixes-postSP5/LSA3-fix/
   NOTE: The above URL has been word-wrapped for readability

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Knowledge Base (KB) article Q231457,
   Malformed Request Causes LSA Service to Hang,
   http://support.microsoft.com/support/kb/articles/q231/4/57.asp.

Obtaining Support on this Issue
===============================
If you require technical assistance with this issue, please contact
Microsoft Technical Support. For information on contacting Microsoft
Technical Support, please see
http://support.microsoft.com/support/contact/default.asp.

Acknowledgments
===============
Microsoft acknowledges BindView Corporation (http://www.bindview.com) for
discovering the vulnerability and reporting it to us.

Revisions
=========
 - June 23, 1999: Bulletin Created.

For additional security-related information about Microsoft products,
please visit http://www.microsoft.com/security


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

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.

(c) 1999 Microsoft Corporation. All rights reserved. Terms of Use.

   *******************************************************************
You have received this e-mail bulletin as a result  of your registration
to the Microsoft Product Security Notification Service.  You may
unsubscribe from this e-mail notification  service at any time by sending
an  e-mail to MICROSOFT_SECURITY-SIGNOFF-REQUEST@ANNOUNCE.MICROSOFT.COM
The subject line and message body are not used in processing the request,
and can be anything you like.

For more information on the Microsoft Security Notification Service
please visit http://www.microsoft.com/security/bulletin.htm.  For
security-related information about Microsoft products, please visit the
Microsoft Security Advisor web site at http://www.microsoft.com/security.


2) "CSRSS Worker Thread Exhaustion" Vulnerability

Microsoft Security Bulletin (MS99-021)
- --------------------------------------

Patch Available for "CSRSS Worker Thread Exhaustion" Vulnerability

Originally Posted: June 23, 1999

Summary
=======
Microsoft has released a patch that eliminates a vulnerability in the
Microsoft(r) Windows NT(r) CSRSS process that could be used to create a
denial of service condition against a machine that allows interactive
logons.

Frequently asked questions regarding this vulnerability, its background,
and the patch can be found at
http://www.microsoft.com/security/bulletins/ms99-021faq.asp

Issue
=====
If all worker threads in CSRSS.EXE are occupied awaiting user input, no
other requests can be  serviced, effectively causing the server to hang.
When user input is provided, processing returns to normal. The patch
eliminates the vulnerability by ensuring that the last CSRSS worker thread
services only requests that do not require user input.

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

Patch Availability
==================
The patch is available at ftp://ftp.microsoft.com/bussys/winnt/
winnt-public/fixes/usa/nt40/Hotfixes-PostSP5/CSRSS-fix/
NOTE: A line break has been inserted into the above URL for readability.

More Information
================
Please see the following references for more information related to this
issue.
 - Microsoft Security Bulletin MS99-021: Frequently Asked Questions,
   http://support.microsoft.com/support/bulletins/ms99-021faq.asp.
 - Microsoft Knowledge Base (KB) article Q2133323,
   "Exceeding MaxRequestThreads may Cause Windows NT to Hang",
   http://support.microsoft.com/support/kb/articles/q231/3/23.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 Jeff Sumner for discovering this vulnerability and
reporting it.

Revisions
=========
 - June 23, 1999: Bulletin Created.


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

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.

(c) 1999 Microsoft Corporation. All rights reserved. Terms of Use.

   *******************************************************************
You have received this e-mail bulletin as a result of your registration
To the Microsoft Product Security Notification Service.  You may
unsubscribe from this e-mail notification service at any time by sending
an e-mail to MICROSOFT_SECURITY-SIGNOFF-REQUEST@ANNOUNCE.MICROSOFT.COM
The subject line and message body are not used in processing the request,
and can be anything you like.

For more information on the Microsoft Security Notification Service
please visit http://www.microsoft.com/security/bulletin.htm.  For
security-related information about Microsoft products, please visit the
Microsoft Security Advisor web site at http://www.microsoft.com/security.



[  End Microsoft Advisory  ]

______________________________________________________________________________

CIAC wishes to acknowledge Microsoft Corp. for the information contained in
this bulletin.
______________________________________________________________________________



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