-----BEGIN PGP SIGNED MESSAGE----- __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Ascend Routing Hardware Vulnerabilities March 24, 1998 00:00 GMT Number I-038 ______________________________________________________________________________ PROBLEM: Two vulnerabilities have been identified with the Ascend router. 1) UDP packets to the router. 2) SNMP "read" and "write" community passwords. PLATFORM: Ascend's Pipeline (version 5.0A) and MAX (version 5.0Ap42). DAMAGE: 1) If exploited, an attacker could cause the system to lockup, causing denial of service. 2) If exploited, an attacker could possibly gain root access if they can guess the community password. SOLUTION: 1) Apply workaround. 2) Change the SNMP "read" and "write" community passwords to ones that are difficult to crack. ______________________________________________________________________________ VULNERABILITY The UDP packet vulnerability has been widely exploited. The ASSESSMENT: SNMP password vulnerability if exploited, could be very serious. Attackers could download the entire configuration of the router. With full access to the router, an attacker could use the router to "sniff" the network. ______________________________________________________________________________ [ Start Security Networks Inc. Advisory ] ###### ## ## ###### ## ### ## ## ###### ## # ## ## ## ## ### ## ###### . ## ## . ###### . Secure Networks Inc. Security Advisory March 16, 1998 Security Issues with Ascend Routing Hardware - ------------------------------------------------------------------------------ SYNOPSIS Ascend Communications provides several popular routing and access-server solutions, including the Pipeline access router and the MAX access server. Due to problems in the Ascend operating system that runs on these platforms, it is possible to deny service to networks that depend on them. Additionally, knowledge of the SNMP "write" community (which defaults to "write") enables an attacker to download the entire configuration file of the router, which contains access passwords and other sensitive information. - ------------------------------------------------------------------------------ DESCRIPTION OF DENIAL OF SERVICE PROBLEM Ascend provides a configuration tool for their equipment which enables operators to reconfigure routers via a graphical interface. This tool is called the "Ascend Java Configurator". The Ascend Configurator is capable of locating Ascend routers on a network, using a special probe protocol. In order to locate Ascend routers, the Configurator broadcasts a specially formatted UDP packet to the "discard" port (port 9). Ascend routers listen for these packets and respond with another UDP packet that contains the symbolic name of the router. In this manner, the Configurator can build a list of all Ascend routers on the local network. By sending a specially formatted (but malformed) probe packet to the discard port of an Ascend router, an attacker can cause an Ascend router to lock up. Attackers can easily discover Ascend routers to crash by sending probe packets to the discard port of arbitrary ranges of addresses; only Ascend routers will respond to them. - ------------------------------------------------------------------------------ DESCRIPTION OF SNMP SECURITY ISSUE Ascend routers are manageable by the SNMP protocol. Ascend's SNMP support includes the ability to read and write MIB variables. Ascend's SNMP system is protected by the SNMP community definitions, which act as passwords for SNMP access. By default, the SNMP "read" password is "public", and the SNMP "write" password is "write". An attacker that can guess the SNMP "read" community can read arbitrary MIB variables, and an attacker that can guess the "write" community can set arbitrary MIB variables to new values. Ascend provides a vendor-specific extension MIB. This MIB includes variables specific to Ascend equipment. Among these variables is a group of settings called "sysConfigTftp", which allow the configuration of the router to be manipulated via the TFTP protocol. By writing to these variables with SNMP "set" messages, an attacker can download the entire configuration of the Ascend router. The full configuration of an Ascend router includes the telnet password (knowledge of which allows an attacker to gain telnet access to the Ascend menu interface), all the enhanced access passwords (allowing an attacker to reconfigure the router from the menu interface), network protocol authentication keys (including RADIUS and OSPF keys), usernames and passwords for incoming connections, and usernames, passwords, and dial-up phone numbers for outgoing connections. All of this information is in plaintext. An attacker with full access to an Ascend router can also use it to "sniff" the networks it is attached to. Ascend routers have an extensive (and largely undocumented) debugging interface; functions are included in this interface to obtain hexadecimal dumps of raw Ethernet, ISDN, DS1, and modem traffic. - ------------------------------------------------------------------------------ VULNERABLE SYSTEMS These issues are known to be relevant to Ascend Pipeline and MAX networking equipment. These vulnerabilities have been confirmed in Ascend's operating system at version 5.0Ap42 (MAX) and 5.0A (Pipeline). Ascend's 6.0 operating system disables SNMP "write" access by default. Previous versions of the software enable SNMP "write" access with a default community of "write". - ------------------------------------------------------------------------------ RESOLUTION The denial-of-service issue detailed in this advisory is due to an implementation flaw in Ascend's software. While no immediate fix is available, it is possible to work around this problem by filtering out packets to the UDP discard port (9). Because SNMP "write" access on an Ascend router is equivalent to complete administrative access, it is very important that the community chosen is hard to guess. Deployed Ascend equipment should be checked to ensure that default (or easily guessed) communities are not in use. The SNMP configuration of an Ascend router is available through the menuing system, as "Ethernet...Mod Config...SNMP Options...". - ------------------------------------------------------------------------------ ADDITIONAL INFORMATION These issues were identified originally by Jennifer Myers and Thomas H. Ptacek at Secure Networks, Inc. SNI thanks Kit Knox of CONNECTnet INS, Inc. for his assistance with this work. Information about Ascend Communications is available at their website at http://www.ascend.com. Products mentioned in this advisory are trademarks of Ascend. - ------------------------------------------------------------------------------ ABOUT SECURE NETWORKS, INC. Secure Networks, Inc. (SNI) is a security research and development company based in Calgary, Alberta, Canada. SNI is the largest independent source of full-disclosure security advisories and new vulnerability information in the world. For more information about this or other advisories, contact us at . A PGP key is provided if privacy is required. For the full text of this and all of SNI's other advisories, see our web page at "http://www.secnet.com/advisories/". General information about SNI is available at "http://www.secnet.com". - ------------------------------------------------------------------------------ COPYRIGHT INFORMATION he contents of this advisory are Copyright (C) 1998 Secure Networks Inc, and may be distributed freely provided that no fee is charged for distribution, and that proper credit is given. - ------------------------------------------------------------------------------ [ End Security Networks Inc. Advisory ] ______________________________________________________________________________ _ CIAC wishes to acknowledge the contributions of Secure Networks Inc. 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. IAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 FAX: +1 925-423-8002 STU-III: +1 925-423-2604 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 925-422-8193 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://www.ciac.org/ (or http://ciac.llnl.gov -- they're the same machine) Anonymous FTP: ftp.ciac.org (or ciac.llnl.gov -- they're the same machine) Modem access: +1 (925) 423-4753 (28.8K baud) +1 (925) 423-3331 (28.8K baud) CIAC has several self-subscribing mailing lists for electronic publications: 1. CIAC-BULLETIN for Advisories, highest priority - time critical information and Bulletins, important computer security information; 2. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 3. SPI-NOTES, for discussion of problems and solutions regarding the use of SPI products. Our mailing lists are managed by a public domain software package called Majordomo, which ignores E-mail header subject lines. 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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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