-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Malformed HTR Request Vulnerability June 18, 1999 17:00 GMT Number J-048 ______________________________________________________________________________ PROBLEM: A vulnerability has been identified in Microsoft\256 Internet Information Server (IIS) 4.0. PLATFORM: Windows NT 4 running IIS 4.0. DAMAGE: This vulnerability could allow denial of service attacks, or under certain conditions, allow arbitrary code to be run. SOLUTION: Apply workaround or patch. ______________________________________________________________________________ VULNERABILITY Risk is high. The exploit for this vulnerability has been ASSESSMENT: publicly released. Apply workaround or patch immediately. ______________________________________________________________________________ [ UPDATED June 18, 1999 with patch information from Microsoft ] [ Start Microsoft Advisory ] Microsoft Security Bulletin (MS99-019) - -------------------------------------- Workaround Available for "Malformed HTR Request" Vulnerability Originally Posted: June 15, 1999 Summary ======= Microsoft has released a patch that eliminates a vulnerability in Microsoft (r) Internet Information Server 4.0. The vulnerability could allow denial of service attacks against an IIS server or, under certain conditions, could allow arbitrary code to be run on the server. Microsoft has issued this bulletin to advise customers of steps they can take to protect themselves against this vulnerability. A patch to eliminate this vulnerability is being developed, and an update to this bulletin will be released to advise customers when it is available. Issue ===== IIS supports several file types that require server-side processing. When a web site visitor requests a file of one of these types, an appropriate filter DLL processes it. A vulnerability exists in ISM.DLL, the filter DLL that processes .HTR files. HTR files enable remote administration of user passwords. The vulnerability involves an unchecked buffer in ISM.DLL. This poses two threats to safe operation. The first is a denial of service threat. A malformed request for an .HTR file could overflow the buffer, causing IIS to crash. The server would not need to be rebooted, but IIS would need to be restarted. The second threat would be more difficult to exploit. A carefully-constructed file request could cause arbitrary code to execute on the server via a classic buffer overrun technique. Neither scenario could occur accidentally. This vulnerability does not involve the functionality of the password administration features of .HTR files. While there are no reports of customers being adversely affected by this vulnerability, Microsoft is proactively releasing this bulletin to allow customers to take appropriate action to protect themselves against it. Affected Software Versions ========================== - Microsoft Internet Information Server 4.0 What Microsoft is Doing ======================= Microsoft has provided a workaround that fixes the problem identified. The workaround is discussed below in What Customers Should Do. Microsoft also has sent this security bulletin to customers subscribing to the Microsoft Product Security Notification Service. See http://www.microsoft.com/security/services/bulletin.asp for more information about this free customer service. What Customers Should Do ======================== Microsoft highly recommends that customers disable the script mapping for .HTR files as follows: - From the desktop, start the Internet Service Manager by clicking Start | Programs | Windows NT 4.0 Option Pack | Microsoft Internet Information Server | Internet Service Manager - Double-click "Internet Information Server" - Right-click on the computer name and select Properties - In the Master Properties drop-down box, select "WWW Service", then click the "Edit" button . - Click the "Home Directory" tab, then click the "Configuration" button . - Highlight the line in the extension mappings that contains ".HTR", then click the "Remove" button. - Respond "yes" to "Remove selected script mapping?" say yes, click OK 3 times, close ISM A patch will be available shortly to eliminate the vulnerability altogether. Customers should monitor http://www.microsoft.com/security for an announcement when the patches are available. Microsoft recommends that customers review the IIS Security Checklist at http://www.microsoft.com/security/products/iis/CheckList.asp More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin MS99-019, Workaround Available for "Malformed HTR Request" Vulnerability (The Web-posted version of this bulletin), http://www.microsoft.com/security/bulletins/ms99-019.asp. - IIS Security Checklist, http://www.microsoft.com/security/products/iis/CheckList.asp Obtaining Support on this Issue =============================== If you require technical assistance with this issue, please contact Microsoft Technical Support. For information on contacting Microsoft Technical Support, please see http://support.microsoft.com/support/contact/default.asp. Revisions ========= - June 15, 1999: Bulletin Created. For additional security-related information about Microsoft products, please visit http://www.microsoft.com/security - ------------------------------------------------------------------ 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/bulletin.htm. For security-related information about Microsoft products, please visit the Microsoft Security Advisor web site at http://www.microsoft.com/security. [ End Microsoft Advisory ] [ Start Updated Microsoft Advisory ] Microsoft Security Bulletin (MS99-019) - -------------------------------------- Patch Available for "Malformed HTR Request" Vulnerability Originally Posted: June 15, 1999 Updated: June 17, 1999 Summary ======= This is an update to Microsoft Security Bulletin MS99-019. The purpose of the update is to advise customers of the availability of a patch that eliminates the vulnerability originally discussed, as well as variants that Microsoft has subsequently identified. Microsoft has released a patch that eliminates a vulnerability in Microsoft(r) Internet Information Server 4.0. The vulnerability could allow denial of service attacks against an IIS server or, under certain conditions, could allow arbitrary code to be run on the server. The patch is fully supported, and Microsoft recommends that affected customers download and install it, if appropriate. Issue ===== IIS supports several file types that require server-side processing. When a web site visitor requests a file of one of these types, an appropriate filter DLL processes it. A vulnerability exists in the way that .HTR, .STM and .IDC files are processed. The vulnerability involves an unchecked buffer in the filter DLLs for these file types. This poses two threats to safe operation. The first is a denial of service threat. A malformed request for an .HTR, .STM or .IDC file could overflow the buffer, causing IIS to crash. The server would not need to be rebooted, but IIS would need to be rebooted in order to resume service. The second threat is that a carefully-constructed file request could cause arbitrary code to execute on the server via a classic buffer overrun technique. Neither attack could occur accidentally. While there are no reports of customers being adversely affected by this vulnerability, Microsoft is proactively releasing this patch to allow customers to take appropriate action to protect themselves against it. In addition, web sites that do not require these file types can disable them altogether, as discussed in Microsoft's IIS Security Checklist (http://www.microsoft.com/security/products/iis/CheckList.asp) Affected Software Versions ========================== - Microsoft Internet Information Server 4.0 What Microsoft is Doing ======================= Microsoft has released a patch that fixes the problem identified. The patch is available for download from the site listed below in What Customers Should Do. Microsoft also has sent this security bulletin to customers subscribing to the Microsoft Product Security Notification Service. See http://www.microsoft.com/security/services/bulletin.asp for more information about this free customer service. Microsoft has published the following Knowledge Base (KB) article on this issue: - Microsoft Knowledge Base (KB) article Q234905, An Improperly Formatted HTTP Request Can Cause The Inetinfo Process To Fail, http://support.microsoft.com/support/kb/articles/q234/9/05.asp (Note: It might take 24 hours from the original posting of this bulletin for the KB article to be visible in the Web-based Knowledge Base.) What Customers Should Do ======================== Microsoft highly recommends that customers evaluate the degree of risk that this vulnerability poses to their systems and determine whether to download and install the patch. The patch can be found at: ftp://ftp.microsoft.com/bussys/IIS/iis-public/fixes/usa/ext-fix/. More Information ================ Please see the following references for more information related to this issue. - Microsoft Security Bulletin MS99-019, Patch Available for "Malformed HTR Request" Vulnerability, (The Web-posted version of this bulletin), http://www.microsoft.com/security/bulletins/ms99-019.asp. - Microsoft Knowledge Base (KB) article Q234905, An Improperly Formatted HTTP Request Can Cause The Inetinfo Process To Fail, http://support.microsoft.com/support/kb/articles/q234/9/05.asp. - IIS Security Checklist, http://www.microsoft.com/security/products/iis/CheckList.asp Obtaining Support on this Issue =============================== If you require technical assistance with this issue, please contact Microsoft Technical Support. For information on contacting Microsoft Technical Support, please see http://support.microsoft.com/support/contact/default.asp. Revisions ========= - June 15, 1999: Bulletin Created. - June 17, 1999: Bulletin updated to advise availability of patch for .HTR, .STM, and .IDC files For additional security-related information about Microsoft products, please visit http://www.microsoft.com/security - ------------------------------------------------------------------------ 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/bulletin.htm. For security-related information about Microsoft products, please visit the Microsoft Security Advisor web site at http://www.microsoft.com/security. [ End Microsoft Advisory ] ______________________________________________________________________________ CIAC wishes to acknowledge Microsoft Corp. for the information contained in this bulletin. ______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@llnl.gov For emergencies and off-hour assistance, DOE, DOE contractor sites, and the NIH may contact CIAC 24-hours a day. During off hours (5PM - 8AM PST), use one of the following methods to contact CIAC: 1. Call the CIAC voice number 925-422-8193 and leave a message, or 2. Call 888-449-8369 to send a Sky Page to the CIAC duty person or 3. Send e-mail to 4498369@skytel.com, or 4. Call 800-201-9288 for the CIAC Project Leader. Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ (or http://ciac.llnl.gov -- they're the same machine) Anonymous FTP: ftp.ciac.org (or ciac.llnl.gov -- they're the same machine) Modem access: +1 (925) 423-4753 (28.8K baud) +1 (925) 423-3331 (28.8K baud) CIAC has several self-subscribing mailing lists for electronic publications: 1. CIAC-BULLETIN for Advisories, highest priority - time critical information and Bulletins, important computer security information; 2. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 3. SPI-NOTES, for discussion of problems and solutions regarding the use of SPI products. Our mailing lists are managed by a public domain software package called Majordomo, which ignores E-mail header subject lines. To subscribe (add yourself) to one of our mailing lists, send the following request as the E-mail message body, substituting ciac-bulletin, spi-announce OR spi-notes for list-name: E-mail to ciac-listproc@llnl.gov or majordomo@rumpole.llnl.gov: subscribe list-name e.g., subscribe ciac-bulletin You will receive an acknowledgment email immediately with a confirmation that you will need to mail back to the addresses above, as per the instructions in the email. This is a partial protection to make sure you are really the one who asked to be signed up for the list in question. If you include the word 'help' in the body of an email to the above address, it will also send back an information file on how to subscribe/unsubscribe, get past issues of CIAC bulletins via email, etc. PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) J-038: HP-UX Vulnerabilities (hpterm, ftp) J-039: HP-UX Vulnerabilities (MC/ServiceGuard & MC/LockManager, DES J-040: HP-UX Security Vulnerability in sendmail J-041: Cisco IOS(R) Software Input Access List Leakage with NAT J-042: Web Security J-043: (bulletin in process) J-044: Tru64/Digital UNIX (dtlogin) Security Vulnerability J-045: Vulnerability in statd exposes vulnerability in automountd J-046: HP-UX VVOS NES Vulnerability J-047: The ExploreZip Worm -----BEGIN PGP SIGNATURE----- Version: 4.0 Business Edition iQCVAwUBN2qNmLnzJzdsy3QZAQH2uQP/YxV6usnBHI5sF3vut8dn+u1JSbLsni2O +IiR0kC2axsnlFfbspbcDqfOFLen8O+3C/BneotLTEbRdcN0NEvt9Uqx0Aae/1y5 c1X9TQv/gYX0s0xw12ktWnYeH3TYNIi/wlKiHCyyd0yepvF5rVgZgeDwX4B+6rd3 YjFyfmgbwrI= =75ya -----END PGP SIGNATURE-----