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Microsoft Security Bulletin (MS00-024)
- --------------------------------------

Tool Available for "OffloadModExpo Registry Permissions" Vulnerability


Originally Posted: April 12, 2000

Summary
=======
Microsoft has released a tool that installs tighter permissions on a
Windows NT(r) 4.0 registry key. The default permissions  could allow a
malicious user who can interactively log onto a Windows NT 4.0 machine
to compromise the cryptographic keys of  other users who subsequently
log onto the same machine.

Frequently asked questions regarding this vulnerability and the
patch can be found at
http://www.microsoft.com/technet/security/bulletin/fq00-024.asp

Issue
=====
This vulnerability involves a registry key used by the CryptoAPI Base
CSPs to specify the driver DLL for a hardware  accelerator. By design,
such a DLL would have access to users' public and private keys.
Although only administrators should  have permission to add such a
DLL, the permissions on the key actually would allow any user who
could interactively log onto  the machine to do so. By writing a bogus
DLL and installing it, a malicious user could compromise the keys of
other users who  subsequently used the machine.

The machines primarily at risk would be workstations and terminal
servers. If normal security recommendations are followed,  normal
users will not be allowed to interactively log onto domain
controllers, web servers, database servers, ERP servers,  and other
security-critical machines. Windows NT auditing could be used to
determine who changed the key's value. A tool is  available that
resets the permissions on the affected key to the correct default
values. In addition, it incorporates the  functionality of the tool
provided in Microsoft Security Bulletin MS00-008.

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

NOTE: Windows 2000 is not affected by this vulnerability.

Patch Availability
==================
 - X86:
   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20330
 - Alpha:
   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20331

NOTE: Additional security patches are available at the Microsoft
Download Center

More Information
================
Please see the following references for more information related to
this issue.
 - Frequently Asked Questions: Microsoft Security Bulletin MS00-024,
   http://www.microsoft.com/technet/security/bulletin/fq00-024.asp
 - Microsoft Knowledge Base article Q259496 discusses this issue
   and will be available soon.
 - Microsoft TechNet Security web site,
   http://www.microsoft.com/technet/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 thanks Sergio Tabanelli and Banca Nazionale del Lavoro for
reporting this vulnerability to us and working with us  to protect
customers.

Revisions
=========
 - April 12, 2000: 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.

Last updated April 12, 2000

(c) 2000 Microsoft Corporation. All rights reserved. Terms of use.

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