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May 16, 2000 18:00 GMT
PROBLEM: Microsoft has identified two Denial of Service vulnerabilities
and one file reading vulnerability in Microsoft(r) Internet
Information Server (IIS).
PLATFORM: Platforms running Microsoft IIS 4.0 and 5.0.
DAMAGE: (1) Denial of Service vulnerabilities may be used to slow the
affected web server's responses to it users. (2) The file
reading vulnerability could allow unauthorized disclosure of
fragments of certain types of files.
SOLUTION: Apply the vendor's patches as directed by the advisories.
VULNERABILITY The risk is LOW. The vulnerabilities have been discussed in
ASSESSMENT: public forums. However, none of these vulnerabilities would
allow data to be changed, added or deleted on the server, nor
would they allow administrative control over the machine to be
usurped.
This CIAC bulletin contains Microsoft Security Bulletins MS00-030 and MS00- 031. [ Start of Microsoft Security Bulletin MS00-030 ] Microsoft Security Bulletin (MS00-030) - - -------------------------------------- Patch Available for "Malformed Extension Data in URL" Vulnerability Originally Posted: May 11, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Internet Information Server. The vulnerability could be used to slow the performance of an affected server, or temporarily stop it altogether. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-030.asp Issue ===== In compliance with RFC 2396, the algorithm in IIS that processes URLs has flexibility built in to allow it to process any arbitrary sequence of file extensions or subresource identifiers (referred to in the RFC as path_segments). By providing an URL that contains specially-malformed file extension information, a malicious user could misuse this flexibility in order to arbitrarily increase the work factor associated with parsing the URL. This could consume much or all of the CPU availability on the server and prevent useful work from being done. The vulnerability does not provide any capability to cause the server to fail, or to add, change or delete data on it. Likewise, it provides no capability to usurp administrative control of the web server. The slowdown would only last until the URL had been processed, at which point service would return to normal. Affected Software Versions ========================== - Microsoft Internet Information Server 4.0 - Microsoft Internet Information Server 5.0 Patch Availability ================== - Internet Information Server 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20906 - Internet Information Server 5.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20904 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 MS00-030, http://www.microsoft.com/technet/security/bulletin/fq00-030.asp - Microsoft Knowledge Base article Q260205 discusses this issue and will be available soon. - RFC 2396, Uniform Resource Identifiers (URI): Generic Syntax, http://www.ietf.org/rfc/rfc2396.txt. - 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 Underground Security Systems Research (http://www.ussrback.com) for reporting this vulnerability to us and working with us to protect customers. Revisions ========= - May 11, 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 May 11, 2000 (c) 2000 Microsoft Corporation. All rights reserved. Terms of use. [ End of Microsoft Security Bulletin MS00-030 ] [ Start of Microsoft Security Bulletin MS00-031 ] Microsoft Security Bulletin (MS00-031) - - -------------------------------------- Patch Available for "Undelimited .HTR Request" and "File Fragment Reading via .HTR" Vulnerabilities Originally Posted: May 10, 2000 Summary ======= Microsoft has released a patch that eliminates two security vulnerabilities in Microsoft(r) Internet Information Server. The vulnerabilities could, respectively, be used to slow an affected web server's response or to obtain the source code of certain types of files under very restricted conditions. Frequently asked questions regarding these vulnerabilities and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-031.asp Issue ===== This patch eliminates two security vulnerabilities that are unrelated except by virtue of the fact that both exist in the ISAPI extension that provides web-based password administration via .HTR scripts. - The "Undelimited .HTR Request" vulnerability is a denial of service vulnerability. If a malicious user provided a password change request that was missing an expected delimiter, the algorithm would conduct an unbounded search. This would prevent it from servicing additional .HTR requests, and could also slow the overall response of the server. - The ".HTR File Fragment Reading" vulnerability could allow fragments of certain types of files to be read by providing a malformed request that would cause the .HTR processing to be applied to them. However, the vulnerability could only be exploited under extremely restrictive conditions, and the most valuable data in the files would be the least likely to actually appear in the fragments sent to the user. Neither of these vulnerabilities would allow data to be added, deleted or changed on the server, nor would they allow any administrative control on the server to be usurped. Although .HTR files are used to allow web-based password administration, neither of these vulnerabilities involve any weakness in password handling. Also, if security best practices have been followed, and unneeded script mappings have been removed, many customers will have removed the .HTR script mapping and thus be unaffected by either vulnerability. Affected Software Versions ========================== - Internet Information Server 4.0 - Internet Information Server 5.0 Patch Availability ================== - Internet Information Server 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20905 - Internet Information Server 5.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=20903 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 MS00-031, http://www.microsoft.com/technet/security/bulletin/fq00-031.asp - Microsoft Knowledge Base article Q260838 discusses the "Undelimited .HTR Request" vulnerability and will be available soon. - Microsoft Knowledge Base article Q260069 discusses the "File Fragment Reading via .HTR" vulnerabilty and will be available soon. - How to Change Windows NT Account Passwords Using Internet Information Server (IIS) 4.0, http://www.microsoft.com/technet/support/kb.asp?ID=184619 - 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 Internet Security Systems' X-force (http://xforce.iss.net/), and David Litchfield of Cerberus Information Security, Ltd (http://www.cerberus-infosec.co.uk/), for reporting these vulnerabilities to us, and working with us to protect customers. Revisions ========= - May 10, 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 May 10, 2000 (c) 2000 Microsoft Corporation. All rights reserved. Terms of use. [ End of Microsoft Security Bulletin MS00-031 ]
CIAC wishes to acknowledge the contributions of Microsoft for the information contained in this bulletin.
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