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Cisco 7xx TCP and HTTP Vulnerabilities
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Date: Thu, 11 Mar 1999 16:00:00 -0000 From: [email protected] Reply-To: [email protected] To: [email protected] Subject: Cisco security notice: Cisco 7xx TCP and HTTP vulnerabilities -----BEGIN PGP SIGNED MESSAGE----- Cisco 7xx TCP and HTTP Vulnerabilities ================================================= Revision 1.1 For release 08:00 AM US/Pacific, Thursday, March 11, 1999 Cisco internal use only until release date Summary ======= This notice addresses two unrelated security vulnerabilities in the software used on the Cisco 7xx series of small-office and home-office routers. These vulnerabilities affect only the 7xx series routers (not the 7xxx series); no other Cisco product is affected. The first vulnerability, which has been assigned Cisco bug ID CSCdm03231, can be used to cause system reloads, and therefore denial of service, using TCP connections to the routers' TELNET ports. The second vulnerability has not been assigned a bug ID. 7xx routers running software versions 3.2(5) through 4.2(3) support a simple HTTP server. This HTTP server is enabled by default. Unless the server is explicitly disabled, it can be used to make changes to the router configuration, and/or to gain information about that configuration. This is intentional behavior, but is mentioned in this notice because it appears that customers have been caught unawares by it. There are configuration workarounds for both of these vulnerabilities. Who Is Affected =============== Only networks incorporating 7xx series small-office/home-office routers are affected by these vulnerabilities. 7xx routers are designed to provide network connectivity for small remote networks using ISDN BRI lines. If your network includes 7xx series routers, they are most likely to be found in the homes of network users, or in remote offices with no more than a few employees. CSCdm03231 affects all Cisco 7xx routers, running any software version up to and including release 4.2(3), whose administrators have not taken specific steps to filter incoming TCP connections. Such filtering is not enabled by default. Routers running release 4.3(1) or later software are not affected by CSCdm03231. The HTTP server is present in all software releases from 3.2(5) through 4.2(3), inclusive. The server is enabled by default in all of these software versions. Impact ====== Impact of CSCdm03231 - ------------------ CSCdm03231 permits a remote attacker to force a 7xx router to reload, denying service to the router's home or small office user. It may sometimes be possible to degrade performance without actually inducing a router reload. The attack consumes relatively little bandwidth compared to flooding-based denial of service attacks. In all cases, the router will recover after the attack stops; the attacker must send traffic continuously to maintain denial of service. However, if the router has reloaded, the end user may have to take some installation-dependent action to cause the router to redial the ISDN connection. This vulnerability does not give attackers access to the router CLI, nor does it give them any other way of controlling the router beyond inducing denial of service. Impact of the Presence of the HTTP Server - --------------------------------------- If the HTTP server is enabled, it can be used to change the router's configuration, or to retrieve information about that configuration. No special tools are required. Software Details ================ CSCdm03231 affects all software versions earlier than 4.3(1). Customers with 76x or 77x routers should upgrade to release 4.3(1). Because of memory limitations, release 4.3 is not supported on the 75x routers; customers with 75x routers should use IP filtering as described in the "Workarounds" section. The HTTP server is present in all software versions from 3.2(5) through 4.2(3). It is not present in 3.2(4) or earlier releases, nor is it present in 4.3. Customers with 76x or 77x routers should upgrade to release 4.3(1), primarily because of the desirability of installing the CSCdm03231 fix. The HTTP server may be disabled in any software version; disabling the server is the recommended course of action for customers with 75x routers. Getting Fixed Software - -------------------- Cisco is offering free software upgrades to remedy CSCdm03231 for all vulnerable customers, regardless of contract status. Customers with service contracts may upgrade to any software version, although they may only install the feature sets they've already purchased. Customers without contracts may upgrade to version 4.3(1). Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained via the Software Center on Cisco's Worldwide Web site at http://www.cisco.com. Customers without contracts should get their upgrades by contacting the 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: [email protected] Give the URL of this notice as evidence of your entitlement to a free upgrade. Free upgrades for non-contract customers must be requested through the TAC. Please do not contact either "[email protected]" or "[email protected]" for software upgrades. Workarounds =========== Workaround for CSCdm03231 - ----------------------- CSCdm03231 can be made much less useful to attackers by preventing incoming TCP connections to the router from untrusted hosts. This can be done with the set ip filter profile command, as in the following example: set ip filter tcp source = not trusted-host destination = router block This example would configure the router to accept incoming TCP connections only from a single trusted administrative host. More elaborate configurations, permitting connections of various types from various hosts, are possible; see the router documentation for more information. Disabling the HTTP Server - ----------------------- The HTTP server may be disabled with the system command set clickstart off. Exploitation and Public Announcements ===================================== Cisco knows of no public announcements or discussion of CSCdm03231 before the date of this notice. Cisco has had no reports of malicious exploitation of CSCdm03231. CSCdm03231 was found by an outside security company during laboratory testing. A simple program is needed to effectively exploit CSCdm03231. Although Cisco knows of no program available to the public specifically for this purpose, writing such a program would require very little effort, and only the most basic of skill. Also, certain publicly-available programs intended for other purposes could be used or adapted to exploit the vulnerability. Cisco has had no reports of abuse of the HTTP server on the 7xx series. However, the potential for abuse is discussed in the product documentation, and must be considered to be known to potential attackers. Status of This Notice ===================== This is a final field notice. Although Cisco cannot guarantee the accuracy of all statements in this notice, all the facts have been checked to the best of our ability. Cisco does not anticipate issuing updated versions of this notice unless there is some material change in the facts. Should there be a significant change in the facts, Cisco may update this notice. Distribution - ---------- This notice will be posted on Cisco's Worldwide Web site at http://www.cisco.com/warp/public/770/7xxconn-pub.shtml . In addition to Worldwide Web posting, the initial version of this notice is being sent to the following e-mail and Usenet news recipients: * [email protected] * [email protected] * [email protected] (includes CERT/CC) * Various internal Cisco mailing lists Future updates of this notice, if any, will be placed on Cisco's Worldwide Web server, but may or may not be actively announced on mailing lists or newsgroups. Users concerned about this problem are encouraged to check the URL given above for any updates. Revision History - -------------- Revision 1.0, Initial release candidate version 22:00 US/Pacific 09-MAR-1999 Revision 1.1, Minor editing of software names 09:30 US/Pacific 10-MAR-1999 Cisco Security Procedures ========================= Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's Worlwide Web site at http://www.cisco.com/warp/public/791/sec_incident_response.shtml This includes instructions for press inquiries regarding Cisco security notices. - ------------------------------------------------------------------------ This notice is copyright 1999 by Cisco Systems, Inc. This notice may be redistributed freely after the release date given at the top of the text, provided that redistributed copies are complete and unmodified, including all date and version information. - ------------------------------------------------------------------------ -----BEGIN PGP SIGNATURE----- Version: Big secret iQEVAwUBNuaxtnLSeEveylnrAQEAoQgAnPQwYAa487iEbvIXzQ0WvEbHB0ZlqV6Z j8THdtkyJZtSPATd31JGhQXtHQ1YDuuCC8sV16cPzBFTiWXG0QLErSJD7rpvDHGD nLTHf9dlVD3Yz+lWgJw6S1Y66G0MsRwbAkegXdxdCy/jVm8C4BMLq3Hz4qVY02+A TygTm/jK58ScyVjs3a/6sgxxAQlJYz/QmYyc2hbDqbRtC78Dmr6TAdTJLUOHHfPC hlN9eBeOa8KhT6yDEw65mBtnGxGGj+vgCahyLCUjGWsQMUGJqqY9QcEIXPbmcY10 MAQoaAghzttnhNITXMRli0LQBcakn25g4IX8Oc/q4gk10NE0J09e3A== =oAI6 -----END PGP SIGNATURE----- -----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v0.9.4 (GNU/Linux) Comment: For info see http://www.gnupg.org mQENAzXPH5oC2wEIAMeLeBbPlxIznjaMMKWFlhVgQ85n4wm6A1ZeVCm0D8zRzATl IKC365xXRKx8bwTn5XjKxZ5/XVuZjhsMS/CCa7B4FfxqjYBpEvfWEYDmPfzipTC3 nPAEc3T4yNWfaDKPxqv85WK+3yn0rpygWEgqw8+/n8QvoSbBEA9DU+5RTHIDEfOF vmqtDYB/2luIubN4X2jazwLeGhocarrbZmEW4fKsOpQ1xS1IuWbn9AWXjchMfL8z i+ow9p6BA2I0eqmP/c1Ld+cL/befk3/l8rPA7UUFOn1je7Fng0WAAUvjoHU56fO2 oF6rO5jfHFu6yBt2ouRem/KMzx6WctJ4S97KWesABRG0R0Npc2NvIFN5c3RlbXMg UHJvZHVjdCBTZWN1cml0eSBJbmNpZGVudCBSZXNwb25zZSBUZWFtIDxwc2lydEBj aXNjby5jb20+iQEVAwUTNeY8KkZi51ggEbh5AQE64Af9HKKrj19Z5URxpZu1J/IG LpIJUsix8IHAudPCw/sNc7yipqwHVSDUGu1UKIEnQHP0jeAX98seyMCFdFzxChzc ZbUMXoa0H8nDhlHrAHUKWY66slfdDTBDV8ICdGTOZ9XcQOvoOAL8xhZJ0HTBcdM4 b2w3ECgEdxPiPhL0+gBbqZ4c1YQzVnxKG20G1Vs/NtIJW1nQrapCI5EysQO/srUL u1J/BHsVKfSjayROrQVGWU5pnpxiCr8PRivWFOEXu1xcJLs05wiVvuWmA3x8v8Bt c9xPx3bnpAiiaKOKDqZh0eja6+7/pYWnTdpXwXdS+lwNBneVLLF4I1IOs412BNpa TIkBFQMFEDXPH5py0nhL3spZ6wEBPzgH/Axh9Q8T4Gviyhcqn+pSk+Ug55nkzrvQ +IZx3v9eFbvgBX5q16pRifhniuppTUzkklvOKeQ0Oz7MG6ekDSQcP9PAAJL8Kik5 6MB1HbQTNxkr3qTBJELmXBRT7a6G4F2KzoEbphtS27p4v1MrJ2MWcc5HHrUpD8mE s4x9WhxXfPQSTRmJ9XcvIbv852y1bVMXwISt7TzpQuxH8oBLDhdlQu51ANd7hlAa 7N+M8CYvxmpYCgxlPh8XhAuZZmMSVbtX7TMvoPtFRkwaV0kitxvfch36JMrGK/0b AedGRFGSqa8+bZmCBFABsn+pziHwuXLZhsJ14e8V+zqacxZe2apOQ4mIPwMFEDXP IpCWgad8PVLgfxECuK8AoNBJNor02wuTI9mVACgaknKdSqn9AJ9vZg3u0d5lx3l+ QmkupOtBU40us4kBFQMFEDXPJBwMj7Lhmx7xKQEBhscIAJEkpzdvpzjHfETEZyml eUvq9IO1mVDQDQiyG02akI2PUe39Tl57jKjQ8Lyus0cfvHs7qVc8jj2e1+mUyXA1 AwWOZaJsgVdkZIFKJnU9MfN3XIxwwkg7g3dB99oPrAbTgWkKdodJmTnKsXntAYcm g7/4a5UYujJ2+J/7z1ZmiMtqHu4hU7B36DoxZadmaOPe1cIzsy+5vBgg5vesDLb4 O+3dae6BgsCay0eSLdfLkxI9hTGGiFTHrkgBaxOvQn6oUxVxnJC3EWfasJzFjjxS rXxNuUqL9fRXDNOYH2P9tcQtjOypZPOGgtLvwCf0rQl/6jNxIWTJHk/WXKbunvRK DIS0USBDaXNjbyBTeXN0ZW1zIHByb2R1Y3Qgc2VjdXJpdHkgaW5jaWRlbnQvYnVn IHJlcG9ydGluZyA8c2VjdXJpdHktYWxlcnRAY2lzY28uY29tPokBFQMFEDXPIS9y 0nhL3spZ6wEBGHEH/2CYREeuDDx1lrlqKcTuSn13eyuVasAC4nIRkuY5T+ipAHq0 p2fwQ0QyxGvMD8naoEiTwtO4tHWEfqaqG/txt0draa+//mX/qr865K/4qtDe2n6d Dz3uBy/wUn5i76302dthoUnbHpxug1NkKqop/FHYk9GztBMFlF+5COlBk5fYtYzD 2Nrhc5oA8lPBmJNAcM9ifVIEzYHEnJIcdoqrwGKCz91xxAjW+XnyWtiJ80mRDJx8 88qF5lmmmkopgrxrRwikHprFMsSzT9Vqt3Rts7PtPPOaSBlEcGgKOhN5PcWnpIar MeytrOkctsTjrqMaOEKudgaGgDrIgsBc6iYHwaaIPwMFEDXPIuWWgad8PVLgfxEC L9wAoOo4XEm03MsnyprNhw85ALRew0gZAKD6eXHl1C1ywrNTiWDH0SfR0j9qdokB FQMFEDXPJG8Mj7Lhmx7xKQEBcEQH/2mE5RbDsiZ++EAtWleejNT720qAEUQCtPdj yFRFiNhbc0yUhmoQ9dZKdujxKQWpZJt/5h7ax4VtPm3JtbQz8jgrugJYPYeERQSA qyimvjXwa4AFDsGwC1chtN+HnJwsixpLiHqx8k4CxKtPiKCVjLmZI3n+jZYXtlqb 73pMXOEzOMuKNkM8eteUO29b/h++rN6WPGlS4Ua9t4/sxy7yz6m6FLHzwudub6wl ZfDrBZJuhsOq81j7P+QJ0pAi9fjsyn0Kh4LfjFefcp+9AmRgYFW4N/RTcKLlakkq rj6iCGUMm174zA4vYEohi1ottOEfAxDtF+uLVM5+ONUc6s+1kns= =l8tP -----END PGP PUBLIC KEY BLOCK----- ----------------------------------------------------------------------- Date: Thu, 11 Mar 1999 11:44:28 -0500 From: X-Force <[email protected]> To: [email protected] Subject: ISS Security Advisory: Remote Reconfiguration and Denial of Service Vulnerabilities in Cisco 700 ISDN Routers -----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: [email protected] 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 [email protected] 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 <[email protected]> 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-----