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Microsoft IE "SSL Certificate Validation" Vulnerability



Microsoft IE "SSL Certificate Validation" Vulnerability Privacy and Legal Notice

CIAC INFORMATION BULLETIN

K-049: Microsoft IE "SSL Certificate Validation" Vulnerability

June 6, 2000 18:00 GMT
PROBLEM:       Two vulnerabilities have been identified in the way that
               Microsoft(r) Internet Explorer (IE) handles digital certificates.
PLATFORM:      All systems running:
                - Microsoft Internet Explorer 4.0
                - Microsoft Internet Explorer 4.01
                - Microsoft Internet Explorer 5.0
                - Microsoft Internet Explorer 5.01
DAMAGE:        If exploited, a malicious web site operator could pose as a
               trusted web site.
SOLUTION:      Apply the patch. This patch does require IE 5.01 to install. A
               version for IE 4.01 Service Pack 2 will be released shortly.

VULNERABILITY Risk is low. This vulnerability requires fairly restricted ASSESSMENT: circumstances to be exploited.
[ Start Microsoft's Bulletin ] Microsoft Security Bulletin (MS00-039) --------------------------------------- Patch Available for "SSL Certificate Validation" Vulnerabilities Originally posted: June 05, 2000 Summary ======= Microsoft has released a patch that eliminates two security vulnerabilities in Microsoft(r) Internet Explorer. The vulnerabilities involve how IE handles digital certificates; under a very daunting set of circumstances, they could allow a malicious web site operator to pose as a trusted web site. In addition to eliminating the "SSL Certificate Validation" vulnerabilities, this patch also eliminates all vulnerabilities discussed in Microsoft Security Bulletin MS00-033. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-039.asp Issue ===== Two vulnerabilities have been identified in the way IE handles digital certificates: - When a connection to a secure server is made via either an image or a frame, IE only verifies that the server's SSL certificate was issued by a trusted root - it does not verify the server name or the expiration date. When a connection is made via any other means, all expected validation is performed. - Even if the initial validation is made correctly, IE does not re-validate the certificate if a new SSL session is established with the same server during the same IE session. The circumstances under which these vulnerabilities could be exploited are fairly restricted. In both cases, it is likely that the attacker would need to either carry out DNS cache poisoning or physically replace the server in order to successfully carry out an attack via this vulnerability. The timing would be especially crucial in the second case, as the malicious user would need to poison the cache or replace the machine during the interregnum between the two SSL sessions. Affected Software Versions ========================== - Microsoft Internet Explorer 4.0 - Microsoft Internet Explorer 4.01 - Microsoft Internet Explorer 5.0 - Microsoft Internet Explorer 5.01 Patch Availability ================== - http://www.microsoft.com/windows/ie/download/critical/patch7.htm Note: This patch also eliminates all vulnerabilities discussed in Microsoft Security Bulletin MS00-033. Note: The patch requires IE 5.01 to install; a version that supports IE 4.01 Service Pack 2 will be released shortly. Customers who install this patch on versions other than these may receive a message reading "This update does not need to be installed on this system". This message is incorrect. More information is available in KB article Q254902. 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 MS00-039, http://www.microsoft.com/technet/security/bulletin/fq00-039.asp - Microsoft Knowledge Base article Q254902 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 the ACROS Penetration Team, Slovenia, for reporting this issue to us and working with us to protect customers. Revisions ========= - June 05, 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 June 05,2000 (c) 2000 Microsoft Corporation. All rights reserved. Terms of use. [ End Microsoft's 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:
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                     http://ciac.llnl.gov
                     (same machine -- either one will work)
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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
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