From secnotif@MICROSOFT.COM Fri Oct 13 15:29:40 2000 From: Microsoft Product Security To: BUGTRAQ@SECURITYFOCUS.COM Date: Thu, 12 Oct 2000 20:34:16 -0700 Subject: [BUGTRAQ] Microsoft Security Bulletin (MS00-076) The following is a Security Bulletin from the Microsoft Product Security Notification Service. Please do not reply to this message, as it was sent from an unattended mailbox. ******************************** -----BEGIN PGP SIGNED MESSAGE----- Microsoft Security Bulletin (MS00-076) - -------------------------------------- Patch Available for "Cached Web Credentials" Vulnerability Originally posted: October 12, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Internet Explorer. Under a daunting set of conditions, the vulnerability could enable a malicious user to obtain another user's userid and password to a web site. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-076.asp Issue ===== When a user authenticates to a secured web page via Basic Authentication, IE caches the userid and password that were used, in order to minimize the number of times the user must authenticate to the same site. By design, IE should only send the cached credentials to secured pages on the site. However, it will actually send them to non-secure pages on the site as well. If a malicious user had complete control of another user's network communications, he could wait until another user logged onto a secured site, then spoof a request for a non-secured page in order to collect the credentials. The vulnerability does not provide a means by which the malicious user could force the other user to log onto a secure page of his choice, and could only be used to reveal credentials that had been cached during the current IE session. Affected Software Versions ========================== - Microsoft Internet Explorer 4.x - Microsoft Internet Explorer 5.x prior to version 5.5 Note: Internet Explorer 5.5 is not affected by this vulnerability. Customers using IE 5.5 do not need to take any action. Patch Availability ================== - http://www.microsoft.com/windows/ie/download/critical/q273868.htm Note: The patch requires IE 5.01 SP1 to install. Customers who install this patch on other versions 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 Q273868. Note: As discussed in Affected Software Versions, this vulnerability does not affect IE 5.5. Note: Per the normal security support policy for IE, security patches for Internet Explorer version 4.x are no longer being produced. Microsoft recommends that IE 4.x customers who are concerned about this issue consider upgrading to either IE 5.01 SP1 or IE 5.5. Note: The fix for this issue will be included in IE 5.01 SP2. 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 MS00-076, http://www.microsoft.com/technet/security/bulletin/fq00-076.asp - Microsoft Knowledge Base article Q273868 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 Product Support Services is available at http://support.microsoft.com/support/contact/default.asp. Acknowledgments =============== Microsoft thanks ACROS Security (http://www.acros.si) for reporting this issue to us and working with us to protect customers. Revisions ========= - October 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 October 12, 2000 (c) 2000 Microsoft Corporation. All rights reserved. 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