__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft "Active Setup Download" Vulnerability June 30, 2000 15:00 GMT Number K-057 ______________________________________________________________________________ PROBLEM: The Microsoft Active Setup Control has an internal flaw which allows the downloading of a trusted ".cab" file to any disk location. PLATFORM: All Microsoft systems, except for Windows 2000, running the following software: Microsoft Internet Explorer 4.0 Microsoft Internet Explorer 4.01 Microsoft Internet Explorer 5.0 Microsoft Internet Explorer 5.01 DAMAGE: A malicious web site could download a ".cab" file to any location on a users system, overwriting any system file. The overwriting of system files could render a machine inoperable, creating a denial of service (DoS). SOLUTION: Install the Microsoft patch. ______________________________________________________________________________ VULNERABILITY The risk is MEDIUM. The capability to exploit this vulnerability ASSESSMENT: currently exists. The exploit has been publicly announced. ______________________________________________________________________________ Cabinet File Description Cabinet files have extensions of ".cab". These files have been used by Microsoft and other, as a software distribution medium. Typically a cabinet file contains compressed files, which are automatically decompressed on installation. Within a cabinet file multiple files may be combinded into what is termed a 'folder'. Cabinet files are used to reduce file download size and related download times. Microsoft uses cabinet files in a wide variety of software. Cabinet files may be found in Microsoft service packs, Miscrosoft Powerpoint, Microsoft Office (Windows version), and other products. Large files may span more than one cabinet file. Java and ActiveX commands may be embeded into cabinet files. The running of Java and ActiveX commands are determined by the security permissions used when signing the cabinet file. Cabinet files may be digitally signed in a manner similar to ActiveX Control files. It can be expected that users will continue to encounter cabinet files in the future. [****** Begin Microsoft Bulletin ******] Microsoft Security Bulletin (MS00-042) 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. Terms of use. [****** End Microsoft Bulletin ******] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft 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) 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) K-048: Permissions Problems with FrontPage Extensions K-049: Microsoft IE "SSL Certificate Validation" Vulnerability K-050: NXT BIND 8.2.x Overflow Vulnerability K-051: DoS Vulnerabilities in Kerberos 4 KDC Programs K-052: AIX cdmount Vulnerability K-053: Linux setuid Kernel Fix K-054: Vulnerability in Linux wu-ftpd K-055: HP Web JetAdmin Vulnerability K-056: IRIX WorkShop cvconnect(1M) Vulnerability K-057: Microsoft "Active Setup Download" Vulnerability