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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.076 -- Microsoft Security Bulletin (MS00-027) Patch Available for "Malformed Environment Variable" Vulnerability 03 May 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: CMD.EXE Vendor: Microsoft Operating System: MS Windows NT 4.0 Workstation MS Windows NT 4.0 Server MS Windows NT 4.0 Server, Enterprise Edition MS Windows NT 4.0 Server, Terminal Server Edition MS Windows 2000 Professional MS Windows 2000 Server MS Windows 2000 Advanced Server Platform: N/A Impact: Denial of Service Access Required: Existing User - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Microsoft Security Bulletin (MS00-027) - - -------------------------------------- Patch Available for "Malformed Environment Variable" Vulnerability Originally Posted: April 20, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Windows NT(r) 4.0 and Windows(r) 2000. The vulnerability could allow a malicious user to make some or all of the memory on an affected server unavailable, potentially slowing or stopping an affected server's response time. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-027.asp Issue ===== CMD.EXE, the command processor for Windows NT 4.0 and Windows 2000, has an unchecked buffer in part of the code that handles environment strings. Although we believe that it could not be exploited to run arbitrary code, it could be used to mount denial of service attacks in certain cases. If a server provides batch or other script files, a malicious user could potentially provide arguments that would create an extremely large environment string and overflow the buffer. This would cause the process to fail, and the memory allocated to the process would not be made available again until a dialogue had been cleared on the operator's console. By repeatedly running the batch file, the malicious user could potentially make some or all of the memory on the server temporarily unavailable. As noted above, Microsoft believes that arbitrary code cannot be made to execute via this vulnerability. The machines most likely to be affected would be web servers, as they are the most likely types of machines to offer batch files for use by remote users. However, even an otherwise-affected web server would not be vulnerable to this problem if an operator were present at the console to clear the error dialogue promptly. 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 - Microsoft Windows 2000 Professional - Microsoft Windows 2000 Server - Microsoft Windows 2000 Advanced Server Patch Availability ================== - Windows NT 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20494 - Windows 2000: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20503 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 MS00-027, http://www.microsoft.com/technet/security/bulletin/fq00-027.asp - Microsoft Knowledge Base article Q259622 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 David Litchfield of Cerberus Information Security, Ltd (http://www.cerberus-infosec.co.uk/) for reporting this issue to us and working with us to protect customers. Revisions ========= - April 20, 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 20, 2000 (c) 2000 Microsoft Corporation. All rights reserved. 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