__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Center ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Snort IDS Denial of Service Vulnerability [Internet Security Systems Security Alert] January 29, 2002 18:00 GMT Number M-033 ______________________________________________________________________________ PROBLEM: A remote Denial of Service (DoS) vulnerability exists in Marty Roesch's Snort Intrusion Detection System (IDS). It may be possible for remote attackers to send specially crafted ICMP packets to the program, resulting in a segmentation fault that would crash the Snort engine. PLATFORM: All platforms running Marty Roesch Snort Version 1.8.3 and earlier for all supported platforms. DAMAGE: If launched successfully against a Snort-protected network, all IDS functionality may be disabled until Snort is manually restarted. SOLUTION: All Snort users should install the vendor-supplied patch immediately or upgrade to the latest version of Snort. ______________________________________________________________________________ VULNERABILITY The risk is HIGH. If the attacker can take down your IDS, ASSESSMENT: he/she has taken down one of your lines of defense. Once the IDS is down, you may not be able to identify intrusions into your network. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/033.shtml PATCHES: ISS: http://xforce.iss.net/alerts/advise108.php ______________________________________________________________________________ [***** Start Internet Security Systems Security Alert *****] Internet Security Systems Security Alert January 28, 2002 Remote Denial of Service Vulnerability in Snort IDS Synopsis: Internet Security Systems (ISS) X-Force is aware of a remote Denial of service (DoS) vulnerability present in Marty Roesch’s Snort Intrusion Detection System (IDS). It may be possible for remote attackers to send specially crafted ICMP packets to the program, resulting in a segmentation fault that would crash the Snort engine. This attack can be launched from any routable address, and if launched successfully against a Snort-protected network, all IDS functionality may be disabled until Snort is manually restarted. Affected Versions: Marty Roesch Snort Version 1.8.3 and earlier for all supported platforms Description: Snort is an open-source Intrusion Detection System designed to be simple and lightweight. Snort has packet logging, protocol analysis, attack signature matching and recognition capabilities and is maintained by Marty Roesch of Snort.org. An exploit has been published that demonstrates a flaw in the ICMP protocol handling functionality. Snort incorrectly handles ICMP "Echo" and ICMP "Echo-Reply" packets that contain less than 5 bytes of ICMP data. If Snort encounters such a packet, it will crash and exit. Packets that are used to exploit this vulnerability can be sent with the "ping" command that is present on most operating systems. This exploit technique has been publicly documented, and attackers do not need to have access to the target network or possess knowledge of its configuration. Recommendations: ISS X-Force recommends that all Snort users install the vendor-supplied patch immediately or upgrade to the latest version of Snort. To apply a source code patch to your Snort package: 1. Locate the "decode.h" file in your source distribution. 2. Enter the directory containing decode.h. 3. To update your decode.h file, create a file named "decode.diff", containing the following text: --- olddecode.h Thu Jan 10 15:47:48 2002 +++ decode.h Thu Jan 10 12:15:33 2002 @@ -105,7 +105,7 @@ #define IP_HEADER_LEN 20 #define TCP_HEADER_LEN 20 #define UDP_HEADER_LEN 8 -#define ICMP_HEADER_LEN 8 +#define ICMP_HEADER_LEN 4 #define TH_FIN 0x01 #define TH_SYN 0x02 4. Apply the source code update using the "patch" command, or a similar utility. 5. Build new binaries and reinstall. To upgrade to the latest version of Snort: Use a CVS client to access the Snort CVS server at "cvs.snort.sourceforge.net" with the following command: cvs -d:pserver:anonymous@cvs.snort.sourceforge.net:/cvsroot/snort login Use a blank password when prompted. cvs -z3 -d:pserver:anonymous@cvs.snort.sourceforge.net:/cvsroot/snort co snort Snort’s default configuration does not have the ability to restart when it crashes. ISS X-Force advises all Snort users to develop this functionality using freely available watchdog process monitors, cronjobs, or shell scripts. For more information about applying source code patches or upgrading Snort, please refer to the "SNORT FAQ" document available at: http://www.snort.org. Additional Information: ISS X-Force Database, http://xforce.iss.net/static/7874.php Marty Roesch Snort, http://www.snort.org Credits: This vulnerability was discovered by Sinbad , and reported to the BugTraq mailing list. ______ About Internet Security Systems (ISS) Internet Security Systems is a leading global provider of security management solutions for the Internet, protecting digital assets and ensuring safe and uninterrupted e-business. With its industry-leading intrusion detection and vulnerability assessment, remote managed security services, and strategic consulting and education offerings, ISS is a trusted security provider to more than 9,000 customers worldwide including 21 of the 25 largest U.S. commercial banks, the top 10 U.S. telecommunications companies, and all major branches of the U.S. Federal Government. Founded in 1994, ISS is headquartered in Atlanta, GA, with additional offices throughout North America and international operations in Asia, Australia, Europe, Latin America and the Middle East. For more information, visit the Internet Security Systems web site at www.iss.net or call 888-901-7477. Copyright (c) 2002 Internet Security Systems, Inc. All rights reserved worldwide. Permission is hereby granted for the redistribution of this Alert electronically. It is not to be edited in any way without express consent of the X-Force. If you wish to reprint the whole or any part of this Alert in any other medium excluding electronic medium, please e-mail xforce@iss.net for permission. Disclaimer The information within this paper may change without notice. Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties with regard to this information. In no event shall the author be liable for any damages whatsoever arising out of or in connection with the use or spread of this information. Any use of this information is at the user's own risk. X-Force PGP Key available at: http://xforce.iss.net/sensitive.php as well as on MIT's PGP key server and PGP.com's key server. Please send suggestions, updates, and comments to: X-Force xforce@iss.net of Internet Security Systems, Inc. [***** End Internet Security Systems Security Alert *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Internet Security Systems, Inc. for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Center, 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 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org 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. 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