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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.175 -- Microsoft Security Bulletin (MS00-044) Patch Available for "Absent Directory Browser Argument" Vulnerability 18 July 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Internet Information Server 4.0 Internet Information Server 5.0 Vendor: Microsoft Operating System: MS Windows Server Platforms Platform: N/A Impact: Denial of Service, Inappropriate Access Access Required: Remote Ref: ESB-2000.088 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Microsoft Security Bulletin (MS00-044) - - -------------------------------------- Patch Available for "Absent Directory Browser Argument" Vulnerability Originally Posted: July 14, 2000 Summary ======= Microsoft has released a patch that eliminates two security vulnerabilities in Microsoft(r) Internet Information Server. In sum, the vulnerabilities could allow a malicious user to stop the web server from providing useful service, or to extract certain types of information from it. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-044.asp Issue ===== There are two vulnerabilities at issue here: - The "Absent Directory Browser Argument" vulnerability. An administrative script installed as part of IIS 3.0 but preserved on upgrade to IIS 4.0 or IIS 5.0 does not correctly handle the case where an expected argument is missing. The absence of the argument causes the script to go into an infinite loop, at which point the script consumes all CPU resources on the server. In addition, the permissions on this tool and several related ones, which were appropriate under IIS 3.0, are inappropriate under IIS 4.0 and 5.0. This could allow web site visitors to use these tools, which provide the ability to view the directory structure on the server. - A new variant on the "File Fragment Reading via .HTR" vulnerability. The original version of this vulnerability was discussed in Microsoft Security Bulletin MS00-031. The new vulnerability differs only in the specific way that it could be exploited - like the original version, the effect of the vulnerability is that fragments of .ASP and other files could potentially be retrieved from the server. As in the original version, the mechanics of the new variant make it likely that the parts of an .ASP file most interesting to a malicious user would be stripped out. Microsoft believes that the most appropriate way to eliminate these vulnerabilities is to remove the script mapping for HTR, as discussed in the IIS 4.0 Security Checklist. Only customers with business-critical HTR scripts should retain the functionality and install the patch. Affected Software Versions ========================== - Microsoft Internet Information Server 4.0 - Microsoft Internet Information Server 5.0 Patch Availability ================== - IIS 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=22709 - IIS 5.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=22708 Note: The patch should only be installed by customers who have a business-critical need for the .HTR functionality. Microsoft recommends that all other customers disable the .HTR functionality altogether, as discussed in the FAQ. Note: Customers who choose to install the patch should also strengthen the permissions on the /scripts/iisadmin folder in each web site on the server, and ensure that only administrators can access it. 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 MS00-044, http://www.microsoft.com/technet/security/bulletin/fq00-044.asp - Microsoft Knowledge Base article Q267559 discusses the "Absent Directory Browser Argument" and will be available soon. - Microsoft Knowledge Base article Q267560 discusses the new variant of the "File Fragment Reading via .HTR" 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 the following customers for working with us to protect customers: - Peter Grundl for reporting the "Absent Directory Browser Argument" issue to us - Zuo Lei for reporting the new variant of the "File Fragment Reading via .HTR" vulnerability to us. Revisions ========= - July 14, 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 14, 2000 (c) 2000 Microsoft Corporation. All rights reserved. Terms of use. - -----BEGIN PGP SIGNATURE----- Version: PGP Personal Privacy 6.5.3 iQEVAwUBOW+fzI0ZSRQxA/UrAQHAuwgAm7LQ79JzQz2+nAZIUwKJsHmjYc15NDCK mn9EpwEm3B8HJS2J4VkFatAS9D4/d9s9c1kehFG0E8CH3OO/MTnwSaB+9qelFlpf P7WflT+1xA5cUWu5V/XHceKiS1eYv6pzePpGpkWUKeCHkB78RXtX3bV6HIa6X+rW CR1YnyejY007hHtmXPI7AXa3gcbVcNSfRNBKPGxCKJB037OWX/6Yn01cN1Vy43TV dkB5SzTKWlMILns2mgTpwl8L2ayFwJrAkEbcYTrB7FOzd+va0Fons7pLz0NpDe/n GGr83QpCODtoymIKwjy8pwpQY8EkJEcy5RaDwHbGAm/x3QMiLNR5ZQ== =MUyC - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. 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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). On call after hours for emergencies. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBOXXUHSh9+71yA2DNAQHyrwP9GaZUv2L8An1vUyUOiDAlgGNywWdDfWGy C8rQw2B+YN4GFesjTYj/KIpfCtKbuFtOQOXOBfvlvVgYFR0pLp2A94bvPFd7/fEU fA2n1eFvsaR+Y3DV6SB6zBX3DDRBtdcEa1XewbqeU/QKMhNyDYsjdoDpCZzRVrx0 kx0Xk/Zj3sY= =AKPE -----END PGP SIGNATURE-----