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CERT® Advisory CA-1998-05 Multiple Vulnerabilities in BIND

Original issue date: April 8, 1998
Last revised: November 16, 1998
Added vendor information for Data General

A complete revision history is at the end of this file.

  1. Inverse Query Buffer Overrun in BIND 4.9 and BIND 8 Releases
  2. Denial-of-Service Vulnerabilities in BIND 4.9 and BIND 8 Releases
  3. Denial-of-Service Vulnerability in BIND 8 Releases

I. Description

This advisory describes three distinct problems in BIND. Topic 1 describes a vulnerability that may allow a remote intruder to gain root access on your name server or to disrupt normal operation of your name server. Topics 2 and 3 deal with vulnerabilities that can allow an intruder to disrupt your name server. Detailed descriptions of each problem and its solutions are included in the individual sections on each topic.

II. Impact

Topic 1: A remote intruder can gain root-level access to your name server.

Topics 2 and 3: A remote intruder is able to disrupt normal operation of your name server.

III. Solution

All three problems can be fixed by upgrading to the latest version of BIND, which may be available from your vendor (see Appendix A of this advisory). Questions about the availability of patches from your vendor should be directed to your vendor.

Additionally, the Internet Software Consortium has announced new publicly available versions of BIND on the BIND WWW page (http://www.isc.org/bind.html) and on the USENET newsgroup comp.protocols.dns.bind.

Additionally, patches are provided for Topics 1 and 3, along with steps to take until you can apply the patch or upgrade to the latest version of BIND.

Topic 1: Inverse Query Buffer Overrun in BIND 4.9 and BIND 8 Releases

1.A. Description

BIND 4.9 releases prior to BIND 4.9.7 and BIND 8 releases prior to 8.1.2 do not properly bounds check a memory copy when responding to an inverse query request. An improperly or maliciously formatted inverse query on a TCP stream can crash the server or allow an attacker to gain root privileges.

1.B. Determining if your system is vulnerable

The inverse query feature is disabled by default, so only the systems that have been explicitly configured to allow it are vulnerable.

BIND 8

    Look at the "options" block in the configuration file (typically /etc/named.conf). If there is a "fake-iquery yes;" line, then the server is vulnerable.
BIND 4.9
    Look at the "options" lines in the configuration file (typically /etc/named.boot). If there is a line containing "fake-iquery", then the server is vulnerable.

    In addition, unlike BIND 8, inverse query support can be enabled when the server is compiled. Examine conf/options.h in the source. If the line #defining INVQ is not commented out, then the server is vulnerable.

1.C. What To Do

To address this problem, you can disable inverse queries, upgrade to BIND 8.1.2 now that it is available, or apply the patch (see below for more information on the patch). We urge you to disable inverse queries until you can take one of the other steps.

Disabling inverse queries

BIND 8
    Disable inverse queries by editing named.conf so that either there is no "fake-iquery" entry in the "options" block or the entry is "fake-iquery no;"
BIND 4.9
    Disable inverse queries by editing named.boot, removing any "fake-iquery" entries on "options" lines. Look at conf/options.h in the source. If INVQ has been defined, comment it out and then rebuild and reinstall the server.
Note: Disabling inverse query support can break ancient versions of nslookup. If nslookup fails, replace it with a version from any BIND 4.9 or BIND 8 distribution.

Fixing the Inverse Query Code

BIND 8 BIND 4.9
    Upgrade to BIND 4.9.7 now that it is available (http://www.isc.org/new-bind.html) or apply the patch at this URL:
    http://www.cert.org/advisories/CA-1998-05/BIND4.9_patch.txt

    This file is not PGP signed. It has the following MD5 checksum: 

    MD5 (BIND4.9_patch.txt) = 32da0db1c27e4d484e6fcb7901267c2f
Notes:
  1. We are asking sites to retrieve the patches via FTP rather than including them in the advisory since our experience is that some mail handling systems translate tabs into spaces. This prevents the patch(1) program from working properly.

  2. We have not PGP signed the files since our experience is that some implementations of PGP during the extraction process will strip spaces from some lines containing whitespace only. This may prevent the patch(1) program from working

Topic 2: Denial-of-Service Vulnerabilities in BIND 4.9 and BIND 8 Releases

2.A. Description

BIND 4.9 releases prior to BIND 4.9.7 and BIND 8 releases prior to 8.1.2 do not properly bounds check many memory references in the server and the resolver. An improperly or maliciously formatted DNS message can cause the server to read from invalid memory locations, yielding garbage record data or crashing the server. Many DNS utilities that process DNS messages (e.g., dig, nslookup) also fail to do proper bounds checking.

2.B. Determining if your system is vulnerable

Any system running BIND 4.9 prior to 4.9.7 or BIND 8 prior to 8.1.2 is vulnerable.

2.C. What To Do

There are no workarounds for these problems.

BIND 8

    Upgrade to BIND 8.1.2 now that it is available.
BIND 4.9
    Upgrade to BIND 4.9.7 now that it is available.

Topic 3: Denial-of-Service Vulnerability in BIND 8 Releases

3.A. Description

Assume that the following self-referential resource record is in the cache on a name server: 
	foo.example.	IN	A	CNAME	foo.example.
The actual domain name used does not matter; the important thing is that the target of the CNAME is the same name. The record could be in the cache either because the server was authoritative for it or because the server is recursive and someone asked for it. Once this record is in the cache, issuing a zone transfer request using its name (e.g., "dig @my_nameserver foo.example. axfr") will cause the server to abort().

Most sites will not contain such a record in their configuration files. However, it is possible for an attacker to engineer such a record into the cache of a vulnerable nameserver and thus cause a denial of service.

3.B. Determining if your system is vulnerable

If the BIND 8 server is not recursive and does not fetch glue, then the problem can be exploited only if the self-referential resource record is in a zone for which the server is authoritative.

If the global zone transfer ACL in the options block has been set to deny access and has no self-referential CNAMEs in its authoritative zones, then the server is not vulnerable.

Otherwise, the server is vulnerable. The nameserver is recursive by default, fetches glue by default, and the default global transfer ACL allows all hosts; so many BIND 8 servers will be vulnerable to this problem.

(Note: the in.named(8) man page mentions that sending a SIGINT to the in.named process will dump the current data base and cache to, by default, /var/tmp/named_dump.db. Some sites may find this useful in looking for self-referential CNAMEs. Please see the in.named(8) man page for further details.)

3.C. What To Do

To address this problem, you can apply the workaround described below, upgrade to BIND 8.1.2, or apply the patch provided at the end of this section. Until you can upgrade or apply the patch, we urge you to use the workaround.

Workaround

First set the global zone transfer ACL to deny access to all hosts by adding the following line to the "options" block: 
           allow-transfer { none; };
Next, explicitly authorize zone transfers for each authoritative zone. For example, if the server was authoritative for "example", adding 
           allow-transfer { any; };
to the "zone" statement for "example" would allow anyone to transfer "example".

None of the domains for which the server is authoritative should have self-referential CNAMEs.

Fixing the Problem

Upgrade to BIND 8.1.2, now that it is available, or apply the patch available from the following URL to the BIND 8.1.1 source:
http://www.cert.org/advisories/CA-1998-05/BIND8.1.1_patch.txt

This file is not PGP signed. It has the following MD5 checksum: 

      MD5 (BIND8.1.1_patch.txt) = 33f9dc2eaf221dd48553f490259c2a8b

Notes:

  1. We are asking sites to retrieve the patches via FTP rather than including them in the advisory since our experience is that some mail handling systems translate tabs into spaces. This prevents the patch(1) program from working properly.

  2. We have not PGP signed the files since our experience is that some implementations of PGP during the extraction process will strip spaces from some lines containing whitespace only. This may prevent the patch(1) program from working properly.

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.

Berkeley Software Design, Inc. (BSDI)

  1. BSD/OS 3.0/3.1 AS SHIPPED is not vulnerable. Sites wishing to enable fake-iquery can install mod M310-025, available at http://www.bsdi.com
  2. BSDI will issue a 3.1 mod when a fix is available.
  3. BSD/OS is not vulnerable, since we ship bind 4.9.

Caldera Corporation

Workaround for Topic 1:
Disable inverse queries by editing named.conf so that either there is no "fake-iquery" entry in the "options" block, or so that the entry is "fake-iquery no;"

Workaround for Topic 2:
A workaround is to set the global zone transfer ACL to deny access to all hosts by adding the following line to the "options" block allow-transfer { none; }; Next, explicitly authorize zone transfers for each authoritative zone.

For example, if the server was authoritative for "example", adding allow-transfer { any; }; to the "zone" statement for "example" would allow anyone to transfer "example".

None of the domains the server is authoritative for should have self-referential CNAMEs.

Correction for both Topics:
The proper solution is to Upgrade to the bind-8.1.1-5 packages. They can be found on Caldera's FTP site at:

ftp://ftp.caldera.com/pub/OpenLinux/updates/1.2/006/RPMS

The corresponding source code can be found at:

ftp://ftp.caldera.com/pub/OpenLinux/updates/1.2/006/SRPMS

The MD5 checksums (from the "md5sum" command) for these packages are:

  • b63ace6eab6eee5cf0608c8a245b5e27 bind-8.1.1-5.i386.rpm
  • 4123b0167f5d5769a87cd2d9542a74b4 bind-doc-8.1.1-5.i386.rpm
  • e1d506cbcc87d7c1de915d94d03281b1 bind-utils-8.1.1-5.i386.rpm
  • eec24c0f816244c4729281867fcebbab bind-8.1.1-5.src.rpm
Upgrade with the following commands:

  • rpm -q bind && rpm -U bind-8.1.1-5.i386.rpm
  • rpm -q bind-utils && rpm -U bind-utils-8.1.1-5.i386.rpm
  • rpm -q bind-doc && rpm -U bind-doc-8.1.1-5.i386.rpm
This and other Caldera security resources are located at:

http://www.caldera.com/tech-ref/security/

Data General

This problem is fixed in revision R4.20MU04 of DG/UX. The following patches are
available for earlier revisions:

Revision        Patch Number
-----------------------------------
R4.20MU01       tcpip_R4.20MU01.p10
R4.20MU02       tcpip_R4.20MU02.p09
R4.20MU03       tcpip_R4.20MU03.p01
R4.11MU05       tcpip_R4.11MU05.p09
R4.12MU03       tcpip_R4.12MU03.p02

Digital Equipment Corporation

Digital is investigating this problem.

FreeBSD, Inc.

We ship with INVQ not defined. This makes us resistent against the first vulnerability. This is true for all release after 2.2.0 (2.1.* releases are vulnerable but should be upgraded anyway). As we do not yet ship BIND 8, we are also not vulnerable to the 3rd vulnerability.

We advise everyone to upgrade to BIND 4.9.7.

Hewlett-Packard Company

See Hewlett-Packard Security Bulletin "Security Vulnerability in BIND on HP-UX", HPSBUX9808-083, dated August 19, 1998, for details concerning the availability of patches.

Hewlett Packard's HP-UX patches/Security Bulletins/Security patches are available via email and/or WWW (via the browser of your choice) on HP's Electronic Support Center (ESC).

To subscribe to automatically receive future NEW HP Security Bulletins from the HP ESC Digest service via electronic mail, do the following:

From your Web browser, access the URL:

http://us-support.external.hp.com (US,Canada,Asia-Pacific, and Latin-America)

http://europe-support.external.hp.com (Europe) 



Login with your user ID and password (or register for one). 
     Remember to save the User ID assigned to you, and your password. 
     Once you are in the Main Menu: 
     To -subscribe- to future HP Security Bulletins, 
       click on "Support Information Digests". 
     To -review- bulletins already released from the main Menu, 
       click on the "Technical Knowledge Database (Security Bulletins 
     only)". 
     Near the bottom of the next page, click on "Browse the HP Security 
     Bulletin Archive". 
     Once in the archive there is another link to our current Security 
     Patch Matrix.  Updated daily, this matrix is categorizes security 
     patches by platform/OS release, and by bulletin topic.

To report new security vulnerabilities, send email to

security-alert@hp.com

Please encrypt any exploit information using the security-alert PGP key, available from your local key server, or by sending a message with a -subject- (not body) of 'get key' (no quotes) to security-alert@hp.com.

IBM Corporation

The version of bind shipped with AIX is vulnerable and the following APARs will be available soon: 
    AIX 4.1.x: IX76958  (fix for Topic 1 only)
    AIX 4.2.x: IX76959  (fix for Topic 1 only)
    AIX 4.3.x: IX76960  (fix for Topic 1 and 3 only)
    AIX 4.3.x: IX76962  (fix for Topic 1, 2, and 3.  This is bind 8.1.2.)
Until the official fixes are available, a temporary patch can be found at:

ftp://aix.software.ibm.com/aix/efixes/security 

    File                sum               md5
    ====================================================================
    named.415.tar.Z     64980   157    0e795380b84bf29385d2d946d10406cb
    named.421.tar.Z     44963   157    15a9a006abf4a9d0a0d3210f16d619e5
    named4.430.tar.Z    48236   115    8377b14f74e207707154a9677906f20a
    named8.430.tar.Z    51175   160    e2db14b7055a7424078456bfbfd9bf2d
Detached PGP signatures are also available with a ".asc" extension.

IBM and AIX are registered trademarks of International Business Machines Corporation.

Internet Software Consortium

The Internet Software Consortium has announced BIND version 8.1.2 and BIND version 4.9.7.

If you are running BIND 8.1.1 or 8.1 you want to upgrade to 8.1.2. If you are still running BIND-4 rather than BIND-8, you need the security patches contained in 4.9.7. But, you should really just run BIND-8.

The security fixes included in these releases fix a stack overrun that could occur if inverse query support was enabled, and a number of denial of service attacks where malformed packets could cause the server to crash.

Links to the kits are available at: http://www.isc.org/new-bind.html.

NEC Corporation

Topic1 - Some systems are vulnerable. Patches will be available soon, especially for UX/4800 R11.x and R13.x.

Topic2 - Some systems are vulnerable. Patches will be available soon after the release of bind-4.9.7, especially for UX/4800 R11.x and R13.x.

Topic3 - We do not ship BIND 8 with our products so we are not vulnerable to this problem.

Patches will be available from ftp://ftp.meshnet.or.jp/pub/48pub/security.

The NetBSD Project

The first problem can be fixed in NetBSD 1.3, 1.3.1, and -current prior to 19980408 with the supplied BIND 4.9.6 patch. A patch will be made available for the second problem shortly (alternatively, upgrading to BIND 4.9.7 or 8.1.2 when available will also solve this problem.) NetBSD is not affected by the third problem.

Red Hat Software, Inc.

Red Hat fixes will be available at:

Red Hat 5.0

i386:
rpm -Uvh ftp://ftp.redhat.com/updates/5.0/i386/bind-4.9.6-7.i386.rpm

alpha:
rpm -Uvh ftp://ftp.redhat.com/updates/5.0/alpha/bind-4.9.6-7.alpha.rpm

Red Hat 4.2

i386:
rpm -Uvh ftp://ftp.redhat.com/updates/4.2/i386/bind-4.9.6-1.1.i386.rpm

alpha:
rpm -Uvh ftp://ftp.redhat.com/updates/4.2/alpha/bind-4.9.6-1.1.alpha.rpm

SPARC:
rpm -Uvh ftp://ftp.redhat.com/updates/4.2/sparc/bind-4.9.6-1.1.sparc.rpm

The Santa Cruz Operation, Inc.

The following SCO products are vulnerable:
  • SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4
  • SCO OpenServer 5.0 (also SCO Internet FastStart)
  • SCO UnixWare 2.1
  • SCO UnixWare 7
SCO CMW+ 3.0 is not vulnerable as BIND/named is not supported on CMW+ platforms.

Binary versions of BIND 4.9.7 will be available shortly from the SCO ftp site:

cover letter - ftp://ftp.sco.com/SSE/sse012.ltr
replacement binaries - ftp://ftp.sco.com/SSE/sse012.tar.Z

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
  • SCO UnixWare 7
For the latest security bulletins and patches for SCO products, please refer to http://www.sco.com/security/ .

Silicon Graphics, Inc.

Silicon Graphics Inc. issued Security Advisory, " IRIX BIND DNS Vulnerabilities," 19980603-02-PX, August 6, 1998.

Patches are available via anonymous FTP and your service/support provider.

The SGI anonymous FTP site is sgigate.sgi.com (204.94.209.1) or its mirror, ftp.sgi.com. Security information and patches can be found in the ~ftp/security and ~ftp/patches directories, respectfully.

For subscribing to the wiretap mailing list and other SGI security related information, please refer to the Silicon Graphics Security Headquarters website located at:

http://www.sgi.com/Support/security

Sun Microsystems, Inc.

Topic 1: Patches will be produced for Solaris 5.3, 5.4, 5.5, 5.5.1 and 5.6.

Topic 2: Patches will be produced for Solaris 5.3, 5.4, 5.5, 5.5.1 and 5.6.

Topic 3: Bug fix will be integrated in the upcoming release of Solaris.

The CERT Coordination Center thanks Bob Halley and Paul Vixie of Vixie Enterprises, who provided most of the text of this advisory.

Reminder:
The Internet Software Consortium will announce new publicly available versions of BIND on the BIND WWW page (http://www.isc.org/bind.html) and on the USENET newsgroup comp.protocols.dns.

This document is available from: http://www.cert.org/advisories/CA-1998-05.html

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
Pittsburgh PA 15213-3890
U.S.A.

CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends.

Using encryption

We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from

If you prefer to use DES, please call the CERT hotline for more information.

Getting security information

CERT publications and other security information are available from our web site

* "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.

NO WARRANTY
Any material furnished by Carnegie Mellon University and the Software Engineering Institute is furnished on an "as is" basis. Carnegie Mellon University makes no warranties of any kind, either expressed or implied as to any matter including, but not limited to, warranty of fitness for a particular purpose or merchantability, exclusivity or results obtained from use of the material. Carnegie Mellon University does not make any warranty of any kind with respect to freedom from patent, trademark, or copyright infringement.

Conditions for use, disclaimers, and sponsorship information

Copyright 1998 Carnegie Mellon University.

Revision History 
Nov. 16, 1998  Added vendor information for Data General.
Aug. 21, 1998  Updated vendor informaton for HP and SGI.
June 19, 1998  Updated vendor informaton for SGI.
June 18, 1998  Added a pointer to more information in the UPDATES section. 
May 21, 1998   Updates were made to the following portions of this advisory:
               III. Solutions
               Topic 1: Inverse Query Buffer Overrun in BIND 4.9 and BIND 8 Releases
                 1.C. What To Do
                 Fixing the Inverse Query Code, Bind 8 and Bind 4.9
               Topic 2: Denial-of-Service Vulnerabilities in BIND 4.9 and BIND 8 Releases
                 2.C. What To Do
               Topic 3: Denial-of-Service Vulnerability in BIND 8 Releases
                 3.C. What To Do
                 Fixing the Problem
               Appendix A - Updated vendor information for Internet Software Consortium

Apr. 16, 1998  Appendix A - Updated vendor information for Caldera
               Corporation.