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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.156 -- Microsoft Security Bulletin (MS00-042) Patch Available for "Active Setup Download" Vulnerability 30 June 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Internet Explorer 4.X & 5.X Vendor: Microsoft Operating System: MS Windows Platform: N/A Impact: Overwrite Arbitrary files Denial of Service Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Patch Available for "Active Setup Download" Vulnerability Originally Posted: June 29, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in an ActiveX control that ships with Microsoft(r) Internet Explorer. The vulnerability could be used to overwrite files on the computer of a user who visited a malicious web site operator's site. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-042.asp Issue ===== The Active Setup Control allows .cab files to be downloaded to a user's computer as part of the installation process for software updates. However, the control has two flaws. First, it treats all Microsoft-signed .cab files as trusted, thereby allowing them to be installed without asking the user's approval. Second, it provides a method by which the caller can specify a download location on the user's hard drive. In combination, these two flaws would allow a malicious web site operator to download a Microsoft-signed .cab file as a means of overwriting a file on the user's machine. By overwriting system files, this could allow the malicious user to render the machine unusable. It is important to note that there is no capability via this vulnerability to actually install the software that has been downloaded - the vulnerability only allows files to be overwritten, in a denial of service attack. System File Protection in Windows 2000 would prevent an attack like this one from being used to overwrite system files. 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/patch8.htm Note: The patch also will be available shortly on WindowsUpdate. When this happens, we will modify this bulletin to provide specific information on obtaining it. Note: The patches require IE 4.01 Service Pack 2 or IE 5.01 to install. Customers using versions prior to 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 Q265258. 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 MS00-042, http://www.microsoft.com/technet/security/bulletin/fq00-042.asp - Microsoft Knowledge Base article Q265258 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 Juan Carlos Garcia Cuartango of Spain for reporting this issue to us and working with us to protect customers. Revisions June 29, 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 29,2000 (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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