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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.181 -- Microsoft Security Bulletin (MS00-046) Patch Available for "Cache Bypass" Vulnerability 21 July 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Outlook Express 4.0 to 5.01 Outlook 97 Outlook 98 Outlook 2000 Vendor: Microsoft Operating System: MS Windows Platform: N/A Impact: Read and Create Arbitrary files Access Required: Remote Ref: ESB-2000.179 ESB-2000.180 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Microsoft Security Bulletin (MS00-046) - - -------------------------------------- Patch Available for "Cache Bypass" Vulnerability Originally Posted: July 20, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Outlook(r) and Outlook Express. The vulnerability could allow a malicious user to send an HTML mail that, when opened, could read, but not add, change or delete, files on the recipient's computer. If coupled with other vulnerabilities, it could potentially be used in more advanced attacks as well. The patch eliminates this vulnerability as well as those discussed in Microsoft Security Bulletins MS00-043 and MS00-045. Customers who already have taken the corrective action discussed in either of these bulletins do not need to take any additional action. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-046.asp Issue ===== By design, an HTML mail that creates a file on the recipient's computer should only be able to create it in the so-called cache. Files in the cache, when opened, do so in the Internet Zone. However, this vulnerability would allow an HTML mail to bypass the cache mechanism and create a file in a known location on the recipient's disk. If an HTML mail created an HTML file outside the cache, it would run in the Local Computer Zone when opened. This could allow it to open a file on the user's computer and send it a malicious user's web site. The vulnerability also could be used as a way of placing an executable file on the user's machine, which the malicious user would then seek to launch via some other means. The vulnerability would not enable the malicious user to add, change or delete files on the user's computer. Only files that can be opened in a browser window, such as .txt, .jpg or .htm files, could be read via this vulnerability, and the malicious user would need to know or guess the full path and file name of every file he wished to read. The vulnerability resides in a component that is shared by Outlook and Outlook Express, and as a result the vulnerability affects both products. A version of the component that is not affected by the vulnerability ships as part of Outlook Express 5.5, and customers who have installed it do not need to take any additional action. Outlook Express 5.5 is available as part of Internet Explorer 5.01 Service Pack 1, and, except when installed on Windows 2000, Internet Explorer 5.5. Affected Software Versions ========================== - Microsoft Outlook Express 4.0 - Microsoft Outlook Express 4.01 - Microsoft Outlook Express 5.0 - Microsoft Outlook Express 5.01 - Microsoft Outlook 97 - Microsoft Outlook 98 - Microsoft Outlook 2000 Patch Availability ================== This vulnerability can be eliminated by taking any of the following actions: - Installing the patch available at http://www.microsoft.com/windows/ie/download/critical/patch9.htm - Performing a default installation of Internet Explorer 5.01 Service Pack 1, http://www.microsoft.com/Windows/ie/download/ie501sp1.htm. - Performing a default installation of Internet Explorer 5.5 (http://www.microsoft.com/windows/ie/download/ie55.htm) on any system except Windows 2000. Note: The patch requires IE 4.01 SP2 (http://www.microsoft.com/windows/ie/download/ie401sp2.htm) or IE 5.01 (http://www.microsoft.com/windows/ie/download/ie501.htm) to install. 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 Q247638. Note: In addition to eliminating the vulnerability at issue here, the steps above also eliminate all vulnerabilities discussed in Microsoft Security Bulletins MS00-043 (http://www.microsoft.com/technet/security/bulletin/MS00-043.asp) and MS00-045 (http://www.microsoft.com/technet/security/bulletin/MS00-045.asp). Customers who already have taken the corrective action discussed in either of these bulletins do not need to take any additional action. Note: Additional security patches are available at the Microsoft Download Center (http://www.microsoft.com/downloads). More Information ================ Please see the following references for more information related to this issue. - Frequently Asked Questions: Microsoft Security Bulletin MS00-046, http://www.microsoft.com/technet/security/bulletin/fq00-046.asp - Microsoft Knowledge Base article Q247638 discusses this vulnerability 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. Revisions ========= - July 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 July 20,2000 (c) 2000 Microsoft Corporation. All rights reserved. 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It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). 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