AUSCERT External Security Bulletin Redistribution
                   ESB-1999.170 -- CERT Advisory CA-99-14
                      Multiple Vulnerabilities in BIND
                              11 November 1999


The CERT Coordination Centre has released the following advisory concerning
multiple vulnerabilities in BIND.  Remote users may execute arbitrary code
with the privilege of the named daemon or impair normal operation of the
daemon on systems with vulnerable versions of BIND.

Under certain circumstances these vulnerabilities may allow remote users
to gain root access or to perform Denial of Service (DoS) attacks against
vulnerable systems.

These vulnerabilities differ from those previously reported in the DNS
Denial of Service related AusCERT Alert AL-1999.004.

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CERT Advisory CA-99-14 Multiple Vulnerabilities in BIND

   Original release date: November 10, 1999
   Last revised: --
   Source: CERT/CC
   A complete revision history is at the end of this file.
Systems Affected

     * Systems running various versions of BIND
I. Description

   Six vulnerabilities have been found in BIND, the popular domain name
   server from the Internet Software Consortium (ISC). One of these
   vulnerabilities may allow remote intruders to gain privileged access
   to name servers.
Vulnerability #1: the "nxt bug"

   Some versions of BIND fail to properly validate NXT records. This
   improper validation could allow an intruder to overflow a buffer and
   execute arbitrary code with the privileges of the name server.
   NXT record support was introduced in BIND version 8.2. Prior versions
   of BIND, including 4.x, are not vulnerable to this problem. The
   ISC-supplied version of BIND corrected this problem in version 8.2.2.
Vulnerability #2: the "sig bug"

   This vulnerability involves a failure to properly validate SIG
   records, allowing a remote intruder to crash named; see the impact
   section for additional details.
   SIG record support is found in multiple versions of BIND, including
   4.9.5 through 8.x.
Vulnerability #3: the "so_linger bug"

   By intentionally violating the expected protocols for closing a TCP
   session, remote intruders can cause named to pause for periods up to
   120 seconds.
Vulnerability #4: the "fdmax bug"

   Remote intruders can consume more file descriptors than BIND can
   properly manage, causing named to crash.
Vulnerability #5: the "maxdname bug"

   Improper handling of certain data copied from the network could allow
   a remote intruder to disrupt the normal operation of your name server,
   possibly including a crash.
Vulnerability #6: the "naptr bug"

   Some versions of BIND fail to validate zone information loaded from
   disk files. In environments with unusual combinations of permissions
   and protections, this could allow an intruder to crash named.
Other recent BIND-related vulnerabilities

   AusCERT recently published a report describing denial-of-service
   attacks against name servers. These attacks are unrelated to the
   issues described in this advisory. For information on the
   denial-of-service attacks described by AusCERT, please see AusCERT
   Alert AL-1999.004 available at:
II. Impact

Vulnerability #1

   By exploiting this vulnerability, remote intruders can execute
   arbitrary code with the privileges of the user running named,
   typically root.
Vulnerabilities #2, #4, and #5

   By exploiting these vulnerabilities, remote intruders can disrupt the
   normal operation of your name server, possibly causing a crash.
Vulnerability #3

   By periodically exercising this vulnerability, remote intruders can
   disrupt the ability of your name server to respond to legitimate
   queries. By intermittently exercising this vulnerability, intruders
   can seriously degrade the performance of your name server.
Vulnerability #6

   Local intruders who gain write access to your zone files can cause
   named to crash.
III. Solution

Apply a patch from your vendor or update to a later version of BIND

   Many operating system vendors distribute BIND with their operating
   system. Depending on your support procedures, arrangements, and
   contracts, you may wish to obtain BIND from your operating system
   vendor rather than directly from ISC.
   Appendix A contains information provided by vendors for this advisory.
   We will update the appendix as we receive more information. If you do
   not see your vendor's name, the CERT/CC did not hear from that vendor.
   Please contact your vendor directly.
Appendix A. Vendor Information

Vendor Name


   See ftp://ftp.calderasystems.com/pub/OpenLinux/updates/2.3/current
        db1dda05dbe0f67c2bd2e5049096b42c  RPMS/bind-8.2.2p3-1.i386.rpm
        82bbe025ac091831904c71c885071db1  RPMS/bind-doc-8.2.2p3-1.i386.rpm
        2f9a30444046af551eafd8e6238a50c6  RPMS/bind-utils-8.2.2p3-1.i386.rpm
        0e4f041549bdd798cb505c82a8911198  SRPMS/bind-8.2.2p3-1.src.rpm

Compaq Computer Corporation

   At the time of writing this document, Compaq is currently
   investigating the potential impact to Compaq's BIND release(s).
   As further information becomes available Compaq will provide notice of
   the completion/availability of any necessary patches through AES
   services (DIA, DSNlink FLASH and posted to the Services WEB page) and
   be available from your normal Compaq Services Support channel.
Data General

   We are investigating. We will provide an update when our investigation
   is complete.
Hewlett-Packard Company

   HP is vulnerable, see the chart in the ISC advisory for details on
   your installed version of BIND. Our fix strategy is under
   investigation, watch for updates to this CERT advisory in the CERT
   archives, or an HP security advisory/bulletin.
IBM Corporation

   The bind8 shipped with AIX 4.3.x is vulnerable. We are currently
   working on the following APARs which will be available soon:
   APAR 4.3.x: IY05851
   To Order
   APARs may be ordered using Electronic Fix Distribution (via FixDist)
   or from the IBM Support Center. For more information on FixDist,
   reference URL:
   or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist".
   IBM and AIX are registered trademarks of International Business
   Machines Corporation.
The Internet Software Consortium

   ISC has published an advisory regarding these problems, available at
   The ISC advisory also includes a table summarizing which versions of
   BIND are susceptible to the vulnerabilities described in this

   As far as we know, we don't ship with any of those vulnerabilities.
Santa Cruz Operation, Inc

   Security patches for the following SCO products will be made available
   at http://www.sco.com/security
   OpenServer 5.x.x, UnixWare 7.x.x, UnixWare 2.x.x
Sun Microsystems

   Vulnerability #1
   Solaris 2.3, 2.4, 2.5, 2.5.1, 2.6, and 7 are not vulnerable.
   Vulnerability #2
   Solaris 2.3, 2.4, 2.5, 2.5.1, 2.6, and 7 are not vulnerable.
   Vulnerability #3
   Solaris 2.3, 2.4, 2.5, 2.5.1, and 2.6 are not vulnerable.
          Sun will be producing patches for Solaris 7.
   Vulnerability #4
   Solaris 2.3, 2.4, 2.5, 2.5.1, and 2.6 are not vulnerable.
          Solaris 7 is probably not vulnerable. We are still
   Vulnerability #5
   Solaris 2.3, 2.4, 2.5, 2.5.1, and 2.6 are not vulnerable.
          Sun will be producing patches for Solaris 7.
   Vulnerability #6
   Solaris 2.3, 2.4, 2.5, 2.5.1, and 2.6 are not vulnerable.
          Sun will be producing patches for Solaris 7.
   The CERT Coordination Center would like to thank David Conrad, Paul
   Vixie and Bob Halley of the Internet Software Consortium for notifying
   us of these problems and for their help in constructing the advisory,
   and Olaf Kirch of Caldera for notifying us of some of these problems
   and providing technical assistance and advice.
   This document is available from:
CERT/CC Contact Information

   Email: cert@cert.org
          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
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   CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) / EDT(GMT-4)
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   Conditions for use, disclaimers, and sponsorship information can be
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   Revision History
November 10, 1999:  Initial release

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