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IBM-ERS Security Vulnerability Alert: IBM AIX: Two DoS Vulnerabilities in BIND
From: IGS ERS Advisory Service <advisory () US IBM COM>
Date: Mon, 27 Nov 2000 09:16:32 -0500
IBM Global Services Emergency Response Service Security Vulnerability Alert 27 NOV 2000 11:30 GMT ERS-SVA-E01-2000:005.1 =========================================================================== -----BEGIN PGP SIGNED MESSAGE----- VULNERABILITY SUMMARY VULNERABILITY: Two DoS Vulnerabilities in BIND PLATFORMS: IBM AIX 4.2.x, 4.3.x SOLUTION: Apply the fixes listed below. THREAT: DNS can be completely disrupted on affected servers. CERT Advisory: CA-2000-20 =========================================================================== DETAILED INFORMATION I. Description The Internet Software Consortium, the maintainer of BIND, the software used to provide domain name resolution services, has recently posted information about several denial-of-service vulnerabilities. If exploited, any of these vulnerabilities could allow remote intruders to cause site DNS services to be stopped. For more information about these vulnerabilities, please see http://www.isc.org/products/BIND/bind-security.html Two vulnerabilities in particular are especially serious: The "zxfr bug" Using this vulnerability, attackers on sites which are permitted to request zone transfers can force the named daemon running on vulnerable DNS servers to crash, disrupting name resolution service until the named daemon is restarted. The only preconditions for this attack to succeed is that a compressed zone transfer (ZXFR) request be made from a site allowed to make any zone transfer request (not just ZXFR), and that a subsequent name service query of an authoritative and non-cached record be made. The time between the attack and the crash of named may vary from system to system. This vulnerability has been discussed in public forums. The ISC has confirmed that all platforms running version 8.2.2 of the BIND software prior to patch level 7 are vulnerable to this attack. The "srv bug" This vulnerability can cause affected DNS servers running named to go into an infinite loop, thus preventing further name requests to be handled. This can happen if an SRV record is sent to the vulnerable server. II. Impact Domain name resolution services can be completely negated on DNS servers from remote systems. II. Solutions A. Official fix IBM is working on the following fix which will be available soon: AIX 4.3.x: APAR IY14512 NOTE: Fix will not be provided for versions prior to 4.3 as these are no longer supported by IBM. Affected customers are urged to upgrade to 4.3, or higher. B. How to minimize the vulnerability A temporary fix for AIX 4.3.x systems is available. The temporary fix can be downloaded via ftp from: ftp://aix.software.ibm.com/aix/efixes/security/named8_DoS_efix.tar.Z The MD5 checksums for the efix tarfiles are: Filename sum md5 ================================================================= named43Service.tar 29576 6880 7389bc7758a92f1fccb01fcadbf24166 named43Sgold.tar 28101 6930 b266377a22f869ece15c4046a9827b2a This e-fix contains two tarfiles: named43Service.tar and named43Sgold.tar, each of which contains the files libc.a, named8, and named8-xfer. These are the executables you will need. Choose the tarfile most appropriate for your site. IMPORTANT NOTICE: Your operating system MUST be at this level for the e-fix to work properly and to keep your machines properly operating: fileset bos.net.tcp.server is 4.3.3.25 & bos.rte.libc is 4.3.3.25. You can determine what level your system is at by examining the output from these commands: # lslpp -l bos.rte.libc # lslpp -l bos.net.tcp.server Also, these e-fixes have not been fully regression tested. Customers installing and using these e-fixes do so at their own risk. INSTALLATION STEPS: - - - ---------------------------------------- Perform all steps given below as "root". - - - ---------------------------------------- NOTICE: Test this e-fix FIRST on a test machine (i.e. non-production machine). 1) Setup the test machine with the same data as your production DNS/nameserver has. 2) mkdir /tmp/testnamed 3) cp named43Sgold.tar /tmp/testnamed (or cp named43Sservice.tar /tmp/testnamed) 4) cd /tmp/testnamed 5) tar -xvf *tar 6) mount libc.a /usr/lib/libc.a 7) mount named8 /usr/sbin/named8 8) mount named8-xfer /usr/sbin/named8-xfer 9) startsrc -s named 10) Run some tests to verify the name server's proper operation. 11) If all the tests are successful, then repeat the above on the production machine. We recommend that backup copies of the original "libc.a" and the "named8" files be made. IV. Obtaining Fixes IBM AIX APARs may be ordered using Electronic Fix Distribution (via the FixDist program), or from the IBM Support Center. For more information on FixDist, and to obtain fixes via the Internet, please reference http://techsupport.services.ibm.com/rs6k/fixes.html or send email to "aixserv () austin ibm com" with the word "FixDist" in the "Subject:" line. To facilitate ease of ordering all security related APARs for each AIX release, security fixes are periodically bundled into a cumulative APAR. For more information on these cumulative APARs including last update and list of individual fixes, send email to "aixserv () austin ibm com" with the word "subscribe Security_APARs" in the "Subject:" line. V. Acknowledgements Thanks to the correspondents to BUGTRAQ and the CERT/CC for bringing this vulnerability to our attention. VI. Contact Information Comments regarding the content of this announcement can be directed to: security-alert () austin ibm com To request the PGP public key that can be used to encrypt new AIX security vulnerabilities, send email to security-alert () austin ibm com with a subject of "get key". If you would like to subscribe to the AIX security newsletter, send a note to aixserv () austin ibm com with a subject of "subscribe Security". To cancel your subscription, use a subject of "unsubscribe Security". To see a list of other available subscriptions, use a subject of "help". IBM and AIX are a registered trademark of International Business Machines Corporation. All other trademarks are property of their respective holders. -----BEGIN PGP SIGNATURE----- Version: PGP Personal Privacy 6.5.3 iQCVAwUBOiJUvfWDLGpfj4rlAQHVVgQAs5q9P/l3a64DE91C/V3sRKJOkcj3xP3c 7NUL1I0weiiv1CK2tJsoiLD7pVe9BxupTh6FVzXpHWo5/9RyhgnM/f2ej06nrNPY ab3pE3SICKf5oKkuP045qpOOAkpCr2S7MxgCruIA1ZVH2R/2EfhPCtatGIEeoPPl RK3cgq77KEs= =uTcW -----END PGP SIGNATURE----- =========================================================================== IBM's Internet Emergency Response Service (IBM-ERS) is a subscription-based Internet security response service that includes computer security incident response and management, regular electronic verification of your Internet gateway(s), and security vulnerability alerts similar to this one that are tailored to your specific computing environment. IBM's Virus Emergency Response Service is a subscription-based service that provides assistance with virus risk and emergency management. By acting as an extension of your own internal security staff, IBM-ERS's team of security experts helps you quickly detect and respond to attacks and exposures to your I/T infrastructre. As a part of IBM's Business Continuity Recovery Services organization, the IBM Emergency Response Service is a component of IBM's SecureWay(tm) line of security products and services. From hardware to software to consulting, SecureWay solutions can give you the assurance and expertise you need to protect your valuable business resources. To find out more about the IBM Emergency Response Service, send an electronic mail message to ers-sales () ers ibm com, or call 1-800-426-7378. IBM-ERS maintains a site on the World Wide Web at http://www.ers.ibm.com/. Visit the site for information about the service, copies of security alerts, team contact information, and other items. IBM-ERS uses Pretty Good Privacy* (PGP*) as the digital signature mechanism for security vulnerability alerts and other distributed information. The IBM-ERS PGP* public key is available from http://www.ers.ibm.com/team-info/pgpkey.html. "Pretty Good Privacy" and "PGP" are trademarks of Philip Zimmermann. IBM-ERS is a Member Team of the Forum of Incident Response and Security Teams (FIRST), a global organization established to foster cooperation and response coordination among computer security teams worldwide. Copyright 2000 International Business Machines Corporation. The information in this document is provided as a service to customers of the IBM Emergency Response Service. Neither International Business Machines Corporation, nor any of its employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, complete- ness, or usefulness of any information, apparatus, product, or process contained herein, or represents that its use would not infringe any 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 IBM or its subsidiaries. The views and opinions of authors expressed herein do not necessarily state or reflect those of IBM or its subsidiaries, and may not be used for advertising or product endorsement purposes. The material in this security alert may be reproduced and distributed, without permission, in whole or in part, by other security incident response teams (both commercial and non-commercial), provided the above copyright is kept intact and due credit is given to IBM-ERS. This security alert may be reproduced and distributed, without permission, in its entirety only, by any person provided such reproduction and/or distribution is performed for non-commercial purposes and with the intent of increasing the awareness of the Internet community. ===========================================================================
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