-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Internet Explorer 3.x Vulnerabilities March 10, 1997 22:00 GMT Number H-38a ______________________________________________________________________________ PROBLEM: Arbitrary commands may be executed on a Web client system using Microsoft Internet Explorer 3.x. PLATFORM: Windows 95, Windows NT 4.0 DAMAGE: A Web server can potentially destroy or manipulate data on a visiting client system. SOLUTION: Install the patch referenced below ______________________________________________________________________________ VULNERABILITY These are potentially serious vulnerabilities that should be ASSESSMENT: addressed as soon as possible. ______________________________________________________________________________ Several security vulnerabilities has been discovered in Microsoft Internet Explorer 3.0 and 3.01 for Windows 95 and NT. The vulnerabilities allows an arbitary program to be executed on a user's machine when accessing a malicious Web site. For example, selecting a URL on a Web site could cause the standard Windows calculator to start executing. Other programs, such as format or deltree, might also be executed, which can be more malicious in nature. These programs are executed without permission by the user - the standard security mechanisms provided with Internet Explorer are bypassed completely. These problems are unrelated to ActiveX or Java, common sources of security concern. Rather, these vulnerabilities takes advantage of two features of the Windows 95/NT4.0 interface - shortcuts and hyperlinks. Shortcuts are files ending with a .LNK extension, and provide a means of referencing another file on a system. Windows hyperlinks are files ending with a .URL extension, and provide a quick jump to a URL on the Internet. When files of these types are placed on a Web site, they may potentially execute an arbitary command on the client's computer when accessed through a URL. The arbitary command (and path to the command) must be known ahead of time, but many key system programs are kept in standard locations, so this may be easily guessed. Microsoft has addressed the problems with a patch on their Web site at: http://www.microsoft.com/ie/security/update.htm _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Paul Greene, Geoggrey Elliot, and Brian Morin of Worcester Polytechnic Institute, and 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 has recently formed a new incident response team with CERT and NIST, called FedCIRC. FedCIRC provides computer security services and resources to federal civilian agencies. You can find out more about FedCIRC at http://fedcirc.llnl.gov. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 510-422-8193 FAX: +1 510-423-8002 STU-III: +1 510-423-2604 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), call the CIAC voice number 510-422-8193 and leave a message, or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC duty person, and the secondary PIN number, 8550074 is 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://ciac.llnl.gov/ Anonymous FTP: ciac.llnl.gov (128.115.19.53) Modem access: +1 (510) 423-4753 (28.8K baud) +1 (510) 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. CIAC-NOTES for Notes, a collection of computer security articles; 3. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 4. 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 ListProcessor, which ignores E-mail header subject lines. 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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. 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