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TUCoPS :: Unix :: General :: ciach096.txt

Vulnerability In bind


[ For Public Release ]           

                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                             Vulnerability in Bind
       (Update to Bulletin G-14,  Domain Name Service Vulnerabilities)

August 14, 1997 21:00 GMT                                          Number H-96
PROBLEM:       Domain Name Service (DNS) servers being exploited, using BIND
               and sendmail weaknesses.
PLATFORM:      Systems running any version of BIND before release 8.1.1.
DAMAGE:        Data becomes corrupted ("cache poisoning").
SOLUTION:      Patches or workarounds are available for several platforms. See
VULNERABILITY  Intruders have been able to exploit this vulnerability on DNS
ASSESSMENT:    servers. This vulnerability may potentially extend to other
               network services.

[Start CERT Advisory]

CERT* Advisory CA-97.22
Original issue date: August 13, 1997
Last revised: --

Topic: BIND - the Berkeley Internet Name Daemon
- -----------------------------------------------------------------------------

            *** This advisory supersedes CA-96.02. ***

Several vulnerabilities in the Berkeley Internet Name Daemon (BIND) have been
fixed in the current version of BIND. One of those vulnerabilities is now
being exploited, a vulnerability that results in cache poisoning (malicious
or misleading data from a remote name server is saved [cached] by another
name server). All versions of BIND before release 8.1.1 are vulnerable.

The CERT/CC team recommends installing a patch from your vendor (See Appendix
A). Until you can install a vendor patch, we recommend the workaround
described in Section III.B. We also urge you to take the additional
precautions described in Section III.C.

We will update this advisory as we receive additional information. Please
check our advisory files regularly for updates that relate to your site.

- -----------------------------------------------------------------------------

I.   Description

     The Berkeley Internet Name Daemon (BIND) is an implementation of the
     Domain Name Service (DNS) written primarily for UNIX Systems. BIND
     consists of three parts:

     * The client part. This part contains subroutine libraries used by
       programs that require DNS services. Example clients of these libraries
       are telnet, the X Windows System, and ssh (the secure shell). The
       client part consists of subroutine libraries, header files, and manual

     * The server part. This part contains the name server daemon (named) and
       its support program (named-xfer). These programs provide one source of
       the data used for mapping between host names and IP addresses. When
       appropriately configured, these name server daemons can interoperate
       across a network (the Internet for example) to provide the mapping
       services for that network. The server part consists of the daemon, its
       support programs and scripts, and manual pages.

     * The tools part. This part contains various tools for interrogating
       name servers in a network. They use the client part to extract
       information from those servers. The tools part consists of these
       interrogation tools and manual pages.

     As BIND has matured, several vulnerabilities in the client, server,
     and tools parts have been fixed. Among these is server cache poisoning.
     Cache poisoning occurs when malicious or misleading data received from
     a remote name server is saved (cached) by another name server. This
     "bad" data is then made available to programs that request the cached
     data through the client interface.

     Analysis of recent incidents reported to the CERT Coordination Center
     has shown that the cache poisoning technique is being used to adversely
     affect the mapping between host names and IP addresses. Once this
     mapping has been changed, any information sent between hosts on a
     network may be subjected to inspection, capture, or corruption.

     Although the new BIND distributions do address important security
     problems, not all known problems are fixed. In particular, several
     problems can be fixed only with the use of cryptographic authentication
     techniques. Implementing and deploying this solution is non-trivial;
     work on this task is currently underway within the Internet community.

II.  Impact

     The mapping between host names and IP addresses may be changed. As
     a result, attackers can inspect, capture, or corrupt the information
     exchanged between hosts on a network.

III. Solution

     A.  Obtain and install a patch for this problem.

         Information from vendors can be found in Appendix A of this advisory;
         we will update the appendix as we receive more information.

     B.  Until you are able to install the appropriate patch, we recommend
         the following workaround.

         The "best practice" for operating the publicly available BIND
         system can be either:

         * a heterogeneous solution that involves first installing BIND
           release 4.9.6 and then release 8.1.1, or

         * a homogeneous solution that involves installing only BIND release

         In the paragraphs below, we describe how to determine which solution
         you should use.

         1. Shared Object Client Subroutine Library

            If your system and its programs rely on the shared object client
            subroutine library that comes with some releases of BIND, probably
            named, then you need the shared object subroutine
            library and other client software from release 4.9.6. (As of
            this writing, BIND version 8 does not yet support the client
            part as a shared object library.) This client software is
            available at

                MD5 (bind-4.9.6-REL.tar.gz) = 76dd66e920ad0638c8a37545a6531594

            Follow the instructions in the file named INSTALL in the top-level

            After installing this client part, install the server and tool
            parts from release 8.1.1. This software is available at

                MD5 (bind-src.tar.gz) = 7487b8d647edba2053edc1cda0c6afd0

            Follow the instructions in the src/INSTALL file. Note that
            this version will install the client libraries and header files
            in a non-standard place, /usr/local/lib and /usr/local/include.
            The src/INSTALL file describes what is being installed and

            When you install release 4.9.6 first, its client, server, and
            tools parts will be installed in the production locations. When
            you then install release 8.1.1, the server and tools parts will be
            overwritten by that release's versions, but the 4.9.6 client part
            will not.

         2. No Shared Object Client Subroutine Library

            If you do not need the shared object client subroutine library,
            then you need only upgrade to release 8.1.1. This software is
            available at

                MD5 (bind-src.tar.gz) = 7487b8d647edba2053edc1cda0c6afd0

            Follow the instructions in src/INSTALL. Note that the client
            subroutine library and header files are installed in
            /usr/local/lib and /usr/local/include respectively. To use
            these when building other systems, you will need to refer to
            their installed locations.

        Note: is mirrored in
              Germany at

        As new versions of BIND are released in the future, you will be able
        to find them at these sites, as well as other mirrors. You can also
        check for version

     C. Take additional precautions. 

        As good security practice in general, filter at a router all
        name-based authentication services so that you do not rely on DNS
        information for authentication. This includes the services rlogin, rsh
        (rcp), xhost, NFS, and any other locally installed services that
        provide trust based on domain name information.


Appendix A - Vendor Information

Below is a list of the vendors who have provided information for this
advisory. We will update this appendix as we receive additional information.
If you do not see your vendor's name, the CERT/CC did not hear from that
vendor. Please contact the vendor directly.

Cray Research - A Silicon Graphics Company
  Cray Research has determined that the version of BIND shipped with all
  current releases of Unicos and Unicos/mk are susceptible to the problem
  described in this advisory.  We are currently working on upgrading our
  version of BIND to the 4.9.6 release.

Digital Equipment Corporation
xref CASE ID: SSRT0494U

 At the time of writing this document, patches(binary kits) are in
 progress and final patch testing is expected to begin soon.
 Digital will provide notice of the completion/availability of the
 patches through AES services (DIA, DSNlink FLASH) and be
 available from your normal Digital Support channel.

                                DIGITAL EQUIPMENT CORPORATION   AUG/97
                                -----------------------------   ------

Hewlett-Packard Company
   HP is vulnerable. Patches in process.

IBM Corporation
  IBM is currently working on the following APARs which will be
  available soon:

    AIX 4.1:  IX70236
    AIX 4.2:  IX70237

  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 with a subject of "FixDist".

  IBM and AIX are registered trademarks of International Business Machines

NEC Corporation
   NEC is vulnerable.  The systems affected by this problem
   are as follows:


   Patches are in progress and will be made available from

Siemens-Nixdorf Informationssysteme AG
  We are investigating this problem and will provide updated information
  for this advisory when it becomes available.

The Santa Cruz Operation
   The following SCO operating systems are vulnerable: 

   - SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4
   - SCO OpenServer 5.0
   - SCO UnixWare 2.1

   SCO CMW+ 3.0 is not vulnerable as bind is not supported on CMW+ platforms.

   SCO has made an interim fix available for anonymous ftp: - cover letter - replacement binaries

   The fix includes binaries for the following SCO operating systems:

   - SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4
   - SCO OpenServer 5.0
   - SCO UnixWare 2.1

Sun Microsystems, Inc.
  We are producing patches.

- -----------------------------------------------------------------------------

The CERT Coordination Center staff thanks Paul Vixie and Wolfgang Ley for
their contributions to this advisory.

- -----------------------------------------------------------------------------

If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in the Forum of Incident Response
and Security Teams (see

CERT/CC Contact Information
- -----------------------------

Phone    +1 412-268-7090 (24-hour hotline)
                CERT personnel answer 8:30-5:00 p.m. EST(GMT-5) / EDT(GMT-4)
                and are on call for emergencies during other hours.

Fax      +1 412-268-6989

Postal address
         CERT Coordination Center
         Software Engineering Institute
         Carnegie Mellon University
         Pittsburgh PA 15213-3890

Using encryption
   We strongly urge you to encrypt sensitive information sent by email. We can
   support a shared DES key or PGP. Contact the CERT/CC for more information.
   Location of CERT PGP key

Getting security information
   CERT publications and other security information are available from

   CERT advisories and bulletins are also posted on the USENET newsgroup

   To be added to our mailing list for advisories and bulletins, send
   email to
   In the subject line, type
        SUBSCRIBE  your-email-address

- ----------------------------------------------------------------------------

Copyright 1997 Carnegie Mellon University. Conditions apply; they can be found
in and If you do not have FTP or web access,
send mail to with "copyright" in the subject line.

*CERT is registered in the U.S. Patent and Trademark Office.

- ---------------------------------------------------------------------------

This file:
               click on "CERT Advisories"

Revision history

[End CERT Advisory]


CIAC wishes to acknowledge the contributions of CERT for the
information contained in this bulletin.

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