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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.123 -- Microsoft Security Bulletin (MS00-036) Patch Available for "ResetBrowser Frame" and "HostAnnouncement Flooding" Vulnerabilities 06 June 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: CIFS Vendor: Microsoft Operating System: MS Windows Platform: N/A Impact: Denial of Service Provide Misleading Information Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Microsoft Security Bulletin (MS00-036) - - -------------------------------------- Patch Available for "ResetBrowser Frame" and "HostAnnouncement Flooding" Vulnerabilities Originally posted: May 25, 2000 Summary ======= Microsoft has released a patch that eliminates two security vulnerabilities, one affecting Microsoft(r) Windows NT(r) 4.0 and Windows(r) 2000, and the other affecting Windows NT 4.0 only. Under certain conditions, the vulnerability could allow a malicious user to make it difficult or impossible for other users to locate services and computers on a network; in the worst case, it could allow him to provide incorrect information about the same services and computers. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-036.asp Issue ===== Windows NT 4.0 and Windows 2000 implement the CIFS Computer Browser protocol. Two vulnerabilities exist because of the inability of administrators to limit whether Master Browsers respond to certain frames. The two vulnerabilities are: - The "ResetBrowser Frame" vulnerability, which affects both Windows NT 4.0 and Windows 2000. Like most implementations, the Windows implementation provides the ability for a Master Browser to shut down other browsers via the ResetBrowser frame. However, there is no capability to configure a browser to ignore ResetBrowser frames. This could allow a malicious user to shut down browsers on his subnet as a denial of service attack against the browser service, or, in the worst case, to shut down all browsers and declare his machine the new Master Browser. - The "HostAnnouncement Flooding" vulnerability, which does not affect Windows 2000. Because there is no means of limiting the size of the browse table in Windows NT 4.0, a malicious user could send a huge number of bogus HostAnnouncement frames to a Master Browser. The resulting replication traffic could consume most or all of the network bandwidth and cause other problems in processing the table as well. If a firewall were in place and blocking port 138 UDP, neither vulnerability could be exploited by an external user. Even an internal user could only attack browsers on the same subnet as his machine. Normal administrative tools would allow the administrator to determine who had mounted the attack. 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 2000 Professional - Microsoft Windows 2000 Server - Microsoft Windows 2000 Advanced Server NOTE: Windows 95, Windows 98, and Windows NT 4.0 Server, Terminal Server Edition, also provide an implementation of the Computer Browser protocol. However, they are not listed as affected products because the scenario in which these vulnerabilities could be exploited - large networks that rely on computer browsing - are exactly the ones most unlikely to use Windows 95, Windows 98 or Windows NT 4.0 Terminal Servers as master browsers. Patch Availability ================== - Windows NT 4.0 Workstation, Server, and Server, Enterprise Edition: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=21397 - Windows 2000: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=21298 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 MS00-036, http://www.microsoft.com/technet/security/bulletin/fq00-036.asp - Microsoft Knowledge Base article Q262694 discusses this issue and will be available soon. - Microsoft Knowledge Base article Q263307 discusses this issue and will be available soon. - CIFS/E Browser Protocol, http://www.cifs.com/specs/draft-leach-cifs-browser-spec-00.txt - 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 the following people for working with us to protect customers: - COVERT Labs at PGP Security, Inc. (http://www.nai.com/), for reporting the "ResetBrowser Frame" vulnerability to us. - David Litchfield of Cerberus Information Security, Ltd, (http://www.cerberus-infosec.co.uk/) for reporting the "HostAnnouncement Flooding" vulnerability to us. Revisions ========= - May 25, 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 May 25,2000 (c) 2000 Microsoft Corporation. All rights reserved. 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