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ISS Security Advisory: Remote Reconfiguration and Denial ofX-Force (xforceISS.NET)
Thu, 11 Mar 1999 11:44:28 -0500
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-----BEGIN PGP SIGNED MESSAGE----- ISS Security Advisory March 11, 1999 Remote Reconfiguration and Denial of Service Vulnerabilities in Cisco 700 ISDN Routers Synopsis: Internet Security Systems (ISS) X-Force has discovered several vulnerabilities in Cisco Series 700 routers. The Cisco 700 series is popular among corporate users and telecommuters. It is used to support networks in small offices or home offices. It is also recommended by Internet Service Providers (ISPs) for personal ISDN connectivity. Remote attackers may issue commands to the router without authentication. Remote attackers may also deny network connectivity by forcing the router to reboot. Affected Versions: All versions of IOS/700 on all Cisco 700 series routers are vulnerable. The 700 series includes all models in the 760 and 770 series including the 762M, 766M, 772M, and the 776M. All international models in this series are also vulnerable. Description: The Cisco 700 series was formerly known as the Combinet 750 series. Cisco acquired Combinet and repackaged its products as the Cisco 700 series. The Cisco 700 series runs a non-traditional Cisco operating system. This advisory is limited to Cisco 700 series routers only. Attackers may also take advantage of remote reconfiguration vulnerabilities in ClickStart. ClickStart is a small embedded web server in the IOS/700 that allows for easy remote configuration. ClickStart may allow remote attackers to connect to the router via its web server and issue certain commands to the router. Attackers may also learn which type of switch is connected to the router, as well as the telephone numbers for the ISDN lines. Hackers may use this information to launch further attacks. ClickStart does not attempt to authenticate users that connect to the web server, nor does it automatically filter connection attempts from outside the currently configured subnet. The 700s have the ability to filter these attacks. For detailed filtering information, users must refer to Cisco's on-line documentation. Cisco 700 series is vulnerable to remote resource starvation attacks that can immediately force the router to panic and reboot. These attacks can be repeated indefinitely to permanently deny service to the router. The Cisco 700 series is also vulnerable to similar well-known denial of service attacks. Recommendations: The ClickStart option is always set to "on" unless it is explicitly turned off. The following command will disable ClickStart: Router> set clickstart off All affected users are urged to review the "For More Information" section of this advisory. Cisco urges all Cisco 77x and 76x users to upgrade to IOS/700 version 4.3(1). This version is not supported by the Cisco 75x routers. All service contract customers may download updates at the following address: http://www.cisco.com/cgi-bin/tablebuild.pl/760 Non-contract customers should contact Cisco Technical Assistance Center (TAC). TAC contacts are as follows: * +1 800 553 2447 (toll-free from within North America) * +1 408 526 7209 (toll call from anywhere in the world) * e-mail: taccisco.com For more information: Cisco has compiled a document entitled "Cisco 7xx TCP and HTTP Vulnerabilities" that contains more specific information, as well as workarounds for these vulnerabilities. It is available at the following address: http://www.cisco.com/warp/public/770/7xxconn-pub.shtml More extensive online documentation for the Cisco 700 series is available at: http://www.cisco.com/univercd/cc/td/doc/product/access/acs_fix/750/700cr/ind ex.htm Credits: These vulnerabilities were primarily researched by Dan Ingevaldson of the ISS X-Force. ISS appreciates the assistance of the individuals at Cisco Systems. ________ Copyright (c) 1999 by Internet Security Systems, Inc. Permission is hereby granted for the electronic redistribution of this Security Alert. 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 Summary in any other medium excluding electronic medium, please e-mail xforceiss.net for permission. Internet Security Systems, Inc. (ISS) is the leading provider of adaptive network security monitoring, detection, and response software that protects the security and integrity of enterprise information systems. By dynamically detecting and responding to security vulnerabilities and threats inherent in open systems, ISS's SAFEsuite family of products provide protection across the enterprise, including the Internet, extranets, and internal networks, from attacks, misuse, and security policy violations. ISS has delivered its adaptive network security solutions to organizations worldwide, including firms in the Global 2000, nine of the ten largest U.S. commercial banks, and over 35 governmental agencies. For more information, call ISS at 678-443-6000 or 800-776-2362 or visit the ISS Web site at http://www.iss.net.. 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://www.iss.net/xforce/sensitive.html as well as on MIT's PGP key server and PGP.com's key server. Please send suggestions, updates, and comments to: X-Force <xforceiss.net> of Internet Security Systems, Inc. -----BEGIN PGP SIGNATURE----- Version: 2.6.3a Charset: noconv iQCVAwUBNufrOTRfJiV99eG9AQEmNAP+IgV6LTFvitDCJowQvZee9nzIgCy2hWHK XuuaOPjTonUWIgeEZW9M5M/IDOiyLOh4pHoETRg+LU9zNJ80amCfDNDYDiPYnOok RcPeU5BjMWRJ/nL0yUsbV4TBDCDNHUHUeOSdp7EY25r+aYY6eEpJXc95ERidO7uR PTtElRd+a4M= =aP5D -----END PGP SIGNATURE-----