From psirt@cisco.com Tue May 22 22:14:12 2001 From: Cisco Systems Product Security Incident Response Team To: cust-security-announce@cisco.com Cc: psirt@cisco.com Date: Tue, 22 May 2001 17:52:18 +0100 (BST) Subject: Cisco Security Advisory: -----BEGIN PGP SIGNED MESSAGE----- Cisco Security Advisory: More multiple vulnerabilities in CBOS Revision 1.0 For public release 2001 May 22 08:00 (GMT -0800) ______________________________________________________________________ Summary Multiple vulnerabilities have been identified and fixed in CBOS, an operating system for the Cisco 600 family of routers. * Cisco CBOS Software contains a flaw that permits the successful prediction of TCP Initial Sequence Numbers. It only affects the security of TCP connections that originate or terminate on the affected Cisco device itself; it does not apply to TCP traffic forwarded through the affected device in transit between two other hosts. This vulnerability is documented as Cisco bug ID CSCds16078. * A Cisco 600 router may stop passing the traffic and responding to the console when an ECHO REQUEST packet with the record route option is routed through it. This vulnerability is documented as Cisco bug ID CSCds30150. * Passwords, exec and enable, are stored in the cleartext in the NVRAM. This vulnerability is documented as Cisco bug ID CSCdt04882. * When multiple, large ECHO REPLY packets are routed through an affected Cisco 600 router, it will enter the ROMMON mode and stop passing any further traffic. This vulnerability is documented as Cisco bug ID CSCds74567. The following releases of CBOS are containing all of mentioned vulnerabilities: 2.0.1, 2.1.0, 2.1.0a, 2.2.0, 2.2.1, 2.2.1a, 2.3, 2.3.2, 2.3.5, 2.3.7 and 2.3.8. These vulnerabilities are fixed in the following CBOS releases: 2.3.9, 2.4.1 and 2.4.2. Customers are urged to upgrade to releases that are not vulnerable as shown in detail in the section Software Versions and Fixes below. This advisory is available at the http://www.cisco.com/warp/public/707/CBOS-multiple2-pub.html. Affected Products The affected models are: 627, 633, 673, 675, 675E, 677, 677i and 678. These models are vulnerable if they run any of the following, or earlier, CBOS releases: 2.0.1, 2.1.0, 2.1.0a, 2.2.0, 2.2.1, 2.2.1a, 2.3, 2.3.2, 2.3.5, 2.3.7 and 2.3.8. No other releases of CBOS software are affected by these vulnerabilities. No other Cisco products are affected by these vulnerabilities. These vulnerabilities are fixed in the following CBOS releases: 2.3.9, 2.4.1 and 2.4.2. Details CSCds16078 See also http://www.cisco.com/warp/public/707/ios-tcp-isn-random-pub. shtml TCP sequence numbers are 32-bit integers in the circular range of 0 to 4,294,967,295. The host devices at both ends of a TCP connection exchange an Initial Sequence Number (ISN) selected at random from that range as part of the setup of a new TCP connection. This method provides reasonably good protection against accidental receipt of unintended data. However, to guard against malicious use, it should not be possible for an attacker to infer a particular number in the sequence. If the initial sequence number is not chosen randomly or if it is incremented in a non-random manner between the initialization of subsequent TCP sessions, then it is possible, with varying degrees of success, to forge one half of a TCP connection with another host in order to gain access to that host, or hijack an existing connection between two hosts in order to compromise the contents of the TCP connection. To guard against such compromises, ISNs should be generated as randomly as possible. CSCds30150 By sending ICMP ECHO REQUEST packets (ping) with the IP Record Route option set it is possible to freeze a Cisco 600 router. This can be done either by sending the specially crafted packet or by specifying the "-r" option on the most ping programs. The packet should not be destined to a router itself. CSCdt04882 The exec and enable passwords are stored in the cleartext in NVRAM. Similarly, they are also stored in the cleartext in the configuration file if one is stored on a computer. Anyone who is in a position to see a router's configuration, either directly from the device or in the file on a computer, can learn the passwords. This vulnerability is corrected by storing only an MD5 hash of the password in both NVRAM and in the configuration file, and the plaintext password itself is never retained. CSCds74567 When multiple ICMP ECHO REPLY packets, non standard size, are passed through the affected device the device will stop passing any further traffic. Packets must be larger than the usual size (64 bytes) but that can be easily accomplished either by crafting packets or by adjusting the response size, either via command line or by modifying the program source. Impact CSCds16078 Forged packets can be injected into a network from a location outside its boundary so that they are trusted as authentic by the receiving host, thus resulting in a failure of integrity. Such packets could be crafted to gain access or make some other modification to the receiving system in order to attain some goal, such as gaining unauthorized interactive access to a system or compromising stored data. From a position within the network where it is possible to receive the return traffic (but not necessarily in a position that is directly in the traffic path), a greater range of violations is possible. For example, the contents of a message could be diverted, modified, and then returned to the traffic flow again, causing a failure of integrity and a possible failure of confidentiality. NOTE: Any compromise using this vulnerability is only possible for TCP sessions that originate or terminate on the affected Cisco device itself. It does not apply to TCP traffic that is merely forwarded through the device. CSCds30150 It is possible to cause the Denial-of-Service. CSCdt04882 Anyone who is in a position to see a router's configuration, either directly from the device or in the file on a computer, can learn the exec and enable passwords. Armed with that knowledge, an attacker can log into the device and change the router's configuration. This vulnerability can be even more dangerous if the ISP is using the same passwords for all of the devices which it manages. Such practice, using the same passwords for multiple devices, is strongly discouraged. CSCds74567 It is possible to cause the Denial-of-Service to many affected devices. Software Versions and Fixes The following table summarizes the CBOS software releases affected by the vulnerabilities described in this notice and scheduled dates on which the earliest corresponding fixed releases will be available. +===========+================+=====================================+ | | | | | Release | Description or | Availability of Repaired Releases | | | Platform |=====================================+ | | | General Availability (GA) | +===========+================+=====================================+ | All | All platforms | 2.3.9 | | releases | | 2001-Mart-19 | +-----------+----------------+-------------------------------------+ | All | All platforms | 2.4.1 | | releases | | 2000-December-11 | +-----------+----------------+-------------------------------------+ | All | All platforms | 2.4.2 | | releases | | 2001-May-14 | +===========+================+=====================================+ Obtaining Fixed Software Cisco is offering free software upgrades to eliminate this vulnerability for all affected customers. Customers with contracts should obtain upgraded software through their regular update channels. For most customers, this means that upgrades should be obtained via the point-of-sale or, if they posses a Cisco Connection Online account, they can download it from 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: tac@cisco.com 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 "psirt@cisco.com" or "security-alert@cisco.com" for software upgrades. Workarounds CSCds16078 There is no workaround. CSCds30150 There is no workaround. CSCdt04882 There is no workaround. CSCds74567 There is no workaround. Exploitation and Public Announcements Vulnerabilitiy CSCds30150 has been made public on VULN-DEV list. Altough we have not seen public discussion of vulnerability CSCdt04882 we understand that it is commonly known among users. Vulnerability CSCds74567 has been reported to us by a customer. Status of This Notice: FINAL This is a final notice. Although Cisco cannot guarantee the accuracy of all statements in this notice, all of 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/707/CBOS-multiple2-pub.html. In addition to Worldwide Web posting, a text version of this notice is clear-signed with the Cisco PSIRT PGP key and is posted to the following e-mail and Usenet news recipients: * cust-security-announce@cisco.com * bugtraq@securityfocus.com * first-teams@first.org (includes CERT/CC) * cisco@spot.colorado.edu * comp.dcom.sys.cisco * firewalls@lists.gnac.com * 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 2001-May-22 08:00 GMT-0800 Public release 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 Worldwide Web site at http://www.cisco.com/warp/public/707/sec_incident_response.shtml. This includes instructions for press inquiries regarding Cisco security notices. _________________________________________________________________ This notice is Copyright 2000 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, and include all date and version information. _________________________________________________________________ -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQEVAwUBOwkVc2iN3BRdFxkbAQGo+Af9GyM2CQsJ2lq/sINHZ7xCRKVDSnPcqGOM 9xpr8MMVs30irhJpahaF49lL0gIXiPo83BRykwkuX6lnz/i9qZxiastS0F8IE1iR YBZzxyR1KyODHlDkTycDBF8WS2tEcTv637M/D4sqRJsCbZ6YJe6Q9/hCRoSLLX16 /9U4jvU+J7YCSeZwaOj74EXImzJP4ERUIXmFf6iFkUv8KR+alBqlqHweLQQs6PIT h1hmm5IGT0x94KVZorfxGNmTkbblczuTObUx27LnAfLt1kl4dlLo9VAc6wYVqoU5 ubO4xasMLIwORWG1cFjUGijQdGT3x/DWHD36Syk7hWMkQRRhkTZa4g== =heob -----END PGP SIGNATURE-----