From secnotif@MICROSOFT.COM Fri Dec 3 16:19:58 1999 From: Microsoft Product Security Resent-From: mea culpa To: MICROSOFT_SECURITY@ANNOUNCE.MICROSOFT.COM Resent-To: jericho@attrition.org Date: Thu, 2 Dec 1999 09:14:22 -0800 Subject: Microsoft Security Bulletin (MS99-054) 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. ******************************** Microsoft Security Bulletin (MS99-054) -------------------------------------- Patch Available for "WPAD Spoofing" Vulnerability Originally Posted: December 01, 1999 Summary ======= Microsoft has released a version upgrade that eliminates a vulnerability in Microsoft(r) Internet Explorer 5. Under very specific conditions, the vulnerability could allow a malicious user to provide proxy settings to web clients in another network. Frequently asked questions regarding this vulnerability can be found at http://www.microsoft.com/security/bulletins/MS99-054faq.asp. Issue ===== The IE 5 Web Proxy Auto-Discovery (WPAD) feature enables web clients to automatically detect proxy settings without user intervention. The algorithm used by WPAD prepends the hostname "wpad" to the fully-qualified domain name and progressively removes subdomains until it either finds a WPAD server answering the hostname or reaches the third-level domain. For instance, web clients in the domain a.b.microsoft.com would query wpad.a.b.microsoft, wpad.b.microsoft.com, then wpad.microsoft.com. A vulnerability arises because in international usage, the third-level domain may not be trusted. A malicious user could set up a WPAD server and serve proxy configuration commands of his or her choice. Affected Software Versions ========================== - Microsoft Internet Explorer 5 Patch Availability ================== The vulnerability is eliminated by IE 5.01, which is available at: - http://www.microsoft.com/windows/ie/download/all.htm?bShowPage - http://www.microsoft.com/msdownload/iebuild/ ie501_win32/en/ie501_win32.htm A line break has been inserted into the above URL for readability. More Information ================ Please see the following references for more information related to this issue. - Frequently Asked Questions: Microsoft Security Bulletin MS99-054, http://www.microsoft.com/security/bulletins/ms99-054faq.asp. - Microsoft Knowledge Base (KB) article Q247333, Web Proxy Auto-Discovery "Spoofing" May Change Proxy Settings, http://support.microsoft.com/support/kb/articles/q247/7/33.asp. (Note: It may take 24 hours from the original posting of this bulletin for this KB article to be visible.) - Web Proxy Auto-Discovery Protocol Internet Draft, http://ietf.org/internet-drafts/draft-ietf-wrec-wpad-01.txt. - Microsoft Security Advisor web site, http://www.microsoft.com/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 acknowledges Tim Adam of Open Software Associates (www.osa.com) for bringing this issue to our attention. Revisions ========= - December 01, 1999: 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. (c) 1999 Microsoft Corporation. All rights reserved. Terms of Use. ******************************************************************* You have received this e-mail bulletin as a result of your registration to the Microsoft Product Security Notification Service. You may unsubscribe from this e-mail notification service at any time by sending an e-mail to MICROSOFT_SECURITY-SIGNOFF-REQUEST@ANNOUNCE.MICROSOFT.COM The subject line and message body are not used in processing the request, and can be anything you like. For more information on the Microsoft Security Notification Service please visit http://www.microsoft.com/security/services/bulletin.asp. For security-related information about Microsoft products, please visit the Microsoft Security Advisor web site at http://www.microsoft.com/security.