-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN ICMP vulnerability in Windows 95 and NT 4.0 July 3, 1997 20:00 GMT Number H-78 ______________________________________________________________________________ PROBLEM: A vulnerability in the IP stack on Microsoft Windows systems may allow a remote user to cause a networked system to freeze if exploited ("denial of service"). PLATFORM: Systems running Microsoft Windows 95, Windows NT 4.0 Workstation, and Windows NT 4.0 Server. DAMAGE: If exploited, a remote user may be able to cause a denial-of- service on a networked local machine. The machine be made unresponsive and needs to be rebooted. SOLUTION: Apply vendor patches described below. ______________________________________________________________________________ VULNERABILITY Details of this exploit have been made publicly available and ASSESSMENT: an attack can be successfully executed remotely. ______________________________________________________________________________ Introduction A vulnerability exists in Microsoft Windows 95 and Windows NT 4.0 Server and Workstation operating systems that may lead to a frozen (unresponsive) system if exploited. This denial-of-service attack occurs when a corrupt Internet Control Message Protocol (ICMP) message is sent to a vulnerable system. A series of packets are sent to a vulnerable system which is unable to assemble the packets properly. Problem The operating system may stop responding because the IP stack is unable to resolve the IP packet data that has incorrect offset information. Although this exploit is similar to the Ping of Death attack that appeared earlier this year, this attack uses ICMP instead of IP packets and is not based solely on message size. Solution Microsoft has developed a local patch to updated the TCP/IP protocol stack to correct the problem. Instructions for installing it are available from Microsoft. CIAC recommends that you update your Emergency Repair Disk immedi- ately. For Windows NT 4.0 Server and Workstation: Service Pack 3 must be installed first. Then the ICMP hotfix should be applied. This file can be downloaded from Microsoft at: ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/nt40/hotfixes- postSP3/icmp-fix Windows 95: For Windows 95 and OSR2, this issue is resolved by the file VIP.386 version 4.0.956 (6/30/97) and later. This file is included in the self-extracting VIPUPD.EXE file and can be downloaded from: ftp://ftp.microsoft.com/Softlib/MSLFILES/vipupd.exe ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Microsoft and Russ Cooper 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: +1 510-422-8193 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 (198.128.39.53) 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. 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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) H-68: Windows95 Network Password Vulnerability H-69: Vulnerability in getopt (3) H-70: Vulnerability in rpcbind H-71: Vulnerability in the at(1) program H-72: SunOS eeprom Vulnerability H-73: SunOS chkey Vulnerability H-74: Unix lpr Buffer Overrun Vulnerability H-75: Solaris Solstice AdminSuite Vulnerabilities H-76: Netscape Navigator Security Vulnerability H-77: Microsoft IIS Boundary Condition Vulnerability -----BEGIN PGP SIGNATURE----- Version: 4.0 Business Edition iQCVAwUBM8FzqLnzJzdsy3QZAQHo0gQA9llnfNNC3rU4SHQiu/YjudqTsb+VYXoX O3kX5uIGzTCtLkANly8zjBplE4q+w9In1MCQleV4JXIhOpPoxAl4H3VtW/4n8XKp aibhVPtRsrWH9a6ho/0MB5W2PB36O7wQow0DBzM0ZMspTk9rr/ICMChmt+e5/LhX vAct577LUEA= =XnyT -----END PGP SIGNATURE-----