-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Microsoft IIS "Cookie Marking" Vulnerability October 24, 2000 17:00 GMT Number L-010 _____________________________________________________________________________ PROBLEM: Microsoft IIS 4 and 5 web servers do not implement secure cookies for secure session management. PLATFORM: Microsoft IIS 4 or 5 web servers utilizing active server pages and that have both secure (https) and non-secure (http) web pages. DAMAGE: An intruder with full control of the communications channel between a web browser and a web server serving secure web pages can hijack the user's session. SOLUTION: Users with affected systems should install the patch and then implement secure cookies in their active server page application. _____________________________________________________________________________ VULNERABILITY Risk is LOW. The intruder must have complete control of the ASSESSMENT: communications channel between the web browser and the web server. _____________________________________________________________________________ [****** Start of Microsoft Security Bulletin ******] Microsoft Security Bulletin (MS00-080) - --------------------------------------- Patch Available for "Session ID Cookie Marking" Vulnerability Originally posted: October 23, 2000 Summary ======= Microsoft has released a patch that eliminates a security vulnerability in Microsoft(r) Internet Information Server. The vulnerability could allow a malicious user to "hijack" another user's secure web session, under a very restricted set of circumstances. Frequently asked questions regarding this vulnerability and the patch can be found at http://www.microsoft.com/technet/security/bulletin/fq00-080.asp Issue ===== IIS supports the use of a Session ID cookie to track the current session identifier for a web session. However, .ASP in IIS does not support the creation of secure Session ID cookies as defined in RFC 2109. As a result, secure and non-secure pages on the same web site use the same Session ID. If a user initiated a session with a secure web page, a Session ID cookie would be generated and sent to the user, protected by SSL. But if the user subsequently visited a non-secure page on the same site, the same Session ID cookie would be exchanged, this time in plaintext. If a malicious user had complete control over the communications channel, he could read the plaintext Session ID cookie and use it to connect to the user's session with the secure page. At that point, he could take any action on the secure page that the user could take. The conditions under which this vulnerability could be exploited are rather daunting. The malicious user would need to have complete control over the other user's communications with the web site. Even then, the malicious user could not make the initial connection to the secure page - only the legitimate user could do that. The patch eliminates the vulnerability by adding support for secure Session ID cookies in .ASP pages. (Secure cookies already are supported for all other types of cookies, under all other technologies in IIS). Affected Software Versions ========================== - Microsoft Internet Information Server 4.0 - Microsoft Internet Information Services 5.0 Patch Availability ================== - IIS 4.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=25233 - IIS 5.0: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=25232 Note: The patch installs support for secure Session ID cookies, but does not enable it for reasons of application compatibility. As discussed in the Knowledge Base article, it can be enabled or disabled on a site-by-site basis. Note: - The IIS 4.0 version of this patch can be installed on Windows NT(r) 4.0 systems running Service Pack 6a, and will be included in Service Pack 7. - The IIS 5.0 version of this patch can be installed on Windows(r) 2000 systems with or without Service Pack 1, and will be included in Service Pack 2. 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 MS00-080, http://www.microsoft.com/technet/security/bulletin/fq00-080.asp - Microsoft Knowledge Base article Q274149 discusses this issue and will be available soon. - RFC 2109, HTTP State Management, http://www.ietf.org/rfc/rfc2109.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 Product Support Services is available at http://support.microsoft.com/support/contact/default.asp. Acknowledgments =============== Microsoft thanks ACROS Security (http://www.acros.si/) and Ron Sires and C. Conrad Cady of Healinx (http://www.healinx.com/) for reporting this issue to us and working with us to protect customers. Revisions ========= - October 23, 2000: Bulletin Created. [****** End of Microsoft Security 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-073: Multiple Vulnerabilities in Check Point Firewall-1 L-001: Linux/BSD initialized data overflow in Xlock L-002: Cisco Secure PIX Firewall Mailguard Vulnerability L-003: FreeBSD TCP Sequence Number Vulnerability L-004: FreeBSD LPRng Vulnerability L-005: Linux 'tmpwatch' Vulnerability L-006: HP-UX lpspooler and ftpd Vulnerabilities L-007: Microsoft IIS Folder Traversal L-008: Microsoft HyperTerminal Buffer Overflow L-009: Red Hat Linux "ypbind" Vulnerability -----BEGIN PGP SIGNATURE----- Version: 4.0 Business Edition iQCVAwUBOfXO5rnzJzdsy3QZAQHbEgP/cRSi5hWuQ7WabXYSthAUlwA462IP906w X5FOPcivudV1zIg4knVX2Y97TqVUQEujBEwZAnmD0DGeKI0+Ej0nh9UhdvZpavaC QVfTBunLD0rMdZsLHGdGrG9raCrTasV4Na4O/COqR52ztKEN0bxSljITUCF7s9Al RTvjWuhv1eM= =1Vgd -----END PGP SIGNATURE-----