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CERT Advisory CA-2001-02 Multiple Vulnerabilities in BIND
Original release date: January 29, 2001
Last revised: --
Source: CERT/CC
A complete revision history can be found at the end of this file.
Systems Affected
Domain Name System (DNS) Servers running various versions of ISC BIND
(including both 4.9.x prior to 4.9.8 and 8.2.x prior to 8.2.3; 9.x is
not affected) and derivatives. Because the normal operation of most
services on the Internet depends on the proper operation of DNS
servers, other services could be impacted if these vulnerabilities are
exploited.
Overview
The CERT/CC has recently learned of four vulnerabilities spanning
multiple versions of the Internet Software Consortium's (ISC) Berkeley
Internet Name Domain (BIND) server. BIND is an implementation of the
Domain Name System (DNS) that is maintained by the ISC. Because the
majority of name servers in operation today run BIND, these
vulnerabilities present a serious threat to the Internet
infrastructure.
Three of these vulnerabilities (VU#196945, VU#572183, and VU#868916)
were discovered by the COVERT Labs at PGP Security, who have posted an
advisory regarding these issues at
http://www.pgp.com/research/covert/advisories/047.asp
The fourth vulnerability (VU#325431) was discovered by Claudio
Musmarra.
The Internet Software Consortium has posted information about all four
vulnerabilities at
http://www.isc.org/products/BIND/bind-security.html
I. Description
VU#196945 - ISC BIND 8 contains buffer overflow in transaction
signature (TSIG) handling code
During the processing of a transaction signature (TSIG), BIND 8 checks
for the presence of TSIGs that fail to include a valid key. If such a
TSIG is found, BIND skips normal processing of the request and jumps
directly to code designed to send an error response. Because the
error-handling code initializes variables differently than in normal
processing, it invalidates the assumptions that later function calls
make about the size of the request buffer.
Once these assumptions are invalidated, the code that adds a new
(valid) signature to the responses may overflow the request buffer and
overwrite adjacent memory on the stack or the heap. When combined with
other buffer overflow exploitation techniques, an attacker can gain
unauthorized privileged access to the system, allowing the execution
of arbitrary code.
VU#572183 - ISC BIND 4 contains buffer overflow in nslookupComplain()
The vulnerable buffer is a locally defined character array used to
build an error message intended for syslog. Attackers attempting to
exploit this vulnerability could do so by sending a specially
formatted DNS query to affected BIND 4 servers. If properly
constructed, this query could be used to disrupt the normal operation
of the DNS server process, resulting in either denial of service or
the execution of arbitrary code.
VU#868916 - ISC BIND 4 contains input validation error in
nslookupComplain()
The vulnerable buffer is a locally defined character array used to
build an error message intended for syslog. Attackers attempting to
exploit this vulnerability could do so by sending a specially
formatted DNS query to affected BIND 4 servers. If properly
constructed, this query could be used to disrupt the normal operation
of the DNS server process, resulting in the execution of arbitrary
code.
This vulnerability was patched by the ISC in an earlier version of
BIND 4, most likely BIND 4.9.5-P1. However, there is strong evidence
to suggest that some third party vendors who redistribute BIND 4 have
not included these changes in their BIND packages. Therefore, the
CERT/CC recommends that all users of BIND 4 or its derivatives base
their distributions on BIND 4.9.8.
VU#325431 - Queries to ISC BIND servers may disclose environment
variables
This vulnerability is an information leak in the query processing code
of both BIND 4 and BIND 8 that allows a remote attacker to access the
program stack, possibly exposing program and/or environment variables.
This vulnerability is triggered by sending a specially formatted query
to vulnerable BIND servers.
II. Impact
VU#196945 - ISC BIND 8 contains buffer overflow in transaction
signature (TSIG) handling code
This vulnerability may allow an attacker to execute code with the same
privileges as the BIND server. Because BIND is typically run by a
superuser account, the execution would occur with superuser
privileges.
VU#572183 - ISC BIND 4 contains buffer overflow in nslookupComplain()
This vulnerability can disrupt the proper operation of the BIND server
and may allow an attacker to execute code with the privileges of the
BIND server. Because BIND is typically run by a superuser account, the
execution would occur with superuser privileges.
VU#868916 - ISC BIND 4 contains input validation error in
nslookupComplain()
This vulnerability may allow an attacker to execute code with the
privileges of the BIND server. Because BIND is typically run by a
superuser account, the execution would occur with superuser
privileges.
VU#325431 - Queries to ISC BIND servers may disclose environment
variables
This vulnerability may allow attackers to read information from the
program stack, possibly exposing environment variables. In addition,
the information obtained by exploiting this vulnerability may aid in
the development of exploits for VU#572183 and VU#868916.
III. History
Since 1997, the CERT/CC has published twelve documents describing
vulnerabilities or exploitation of vulnerabilities in BIND with
information and advice on upgrading and preventing compromises.
Unfortunately, many system and network administrators still have not
upgraded their versions of BIND, making them susceptible to a number
of vulnerabilities. Prior vulnerabilities in BIND have been widely
exploited by intruders.
For example, on November 10, 1999, the CERT/CC published CA-1999-14,
which detailed multiple vulnerabilities in BIND. The CERT/CC continued
to receive reports of compromises based on those vulnerabilities
through December 2000. On April 8, 1998, the CERT/CC published
CA-1998-05; reports of compromises based on the vulnerabilities
described therein continued through November of 1998.
The following graph shows the number of incidents reported to the
CERT/CC regarding BIND NXT record (VU#16532) exploits after the
publication of CA-1999-14:
Incidents By Month Involving the BIND NXT Record Vulnerability
(VU#16532)
Based on this past experience, the CERT/CC expects that intruders will
quickly begin developing and using intruder tools to compromise
machines. It is important for IT and security managers to ensure that
their organizations are properly protected before the expected
wide-spread exploitation happens.
Exploitation
The vulnerabilities described in VU#196945, VU#572183, and VU#868916
have been successfully exploited by COVERT Labs in a laboratory
environment. To the best of our knowledge, no exploits have been
released to the public.
IV. Solution
Apply a patch from your vendor
The ISC has released BIND versions 4.9.8 and 8.2.3 to address these
security issues. The CERT/CC recommends that users of BIND 4.9.x or
8.2.x upgrade to BIND 4.9.8, BIND 8.2.3, or BIND 9.1.
Because BIND 4 is no longer actively maintained, the ISC recommends
that users affected by this vulnerability upgrade to either BIND 8.2.3
or BIND 9.1. Upgrading to one of these versions will also provide
functionality enhancements that are not related to security.
The BIND 4.9.8 and 8.2.3 distributions can be downloaded from
ftp://ftp.isc.org/isc/bind/src/
The BIND 9.1 distribution can be downloaded from
ftp://ftp.isc.org/isc/bind9/
Appendix A contains information supplied by ISC and distributors of
BIND. Depending on your local processes, procedures, and expertise,
you may wish to obtain updates from the ISC or from an operating
system vendor who redistributes BIND.
Use Strong Cryptography to Authenticate Services
Services and transactions that rely exclusively on the DNS system for
authentication are inherently weak. We encourage organizations to use
strong cryptography to authenicate services and transactions where
possible. One common use of strong cryptography is the use of SSL in
authenticating and encrypting electronic commerce transactions over
the web. In addition to this use, we encourage organizations to use
SSL, PGP, S/MIME, SSH, and other forms of strong cryptography to
distribute executable content, secure electronic mail, distribute
important information, and protect the confidentiality of all kinds of
data traversing the Internet.
Use Split Horizon DNS to Minimize Impact
It may also be possible to minimize the impact of the exploitation of
these vulnerabilities by configuring your DNS environment to separate
DNS servers used for the public dissemination of information about
your hosts from the DNS servers used by your internal hosts to connect
to other hosts on the Internet. Frequently, different security polices
can be applied to these servers such that even if one server is
compromised the other server will continue to function normally. Split
horizon DNS configuration may also have other security benefits.
References
To read more about the vulnerabilities described in this document,
please visit the CERT/CC Vulnerability Notes Database:
VU#196945 - ISC BIND 8 contains buffer overflow in transaction
signature (TSIG) handling code
http://www.kb.cert.org/vuls/id/196945
VU#572183 - ISC BIND 4 contains buffer overflow in nslookupComplain()
http://www.kb.cert.org/vuls/id/572183
VU#868916 - ISC BIND 4 contains input validation error in
nslookupComplain()
http://www.kb.cert.org/vuls/id/868916
VU#325431 - Queries to ISC BIND servers may disclose environment
variables
http://www.kb.cert.org/vuls/id/325431
To cross-reference CERT/CC VU numbers with other vendor documents via
CVE, please visit
VU#196945 - ISC BIND 8 contains buffer overflow in transaction
signature (TSIG) handling code
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0010
VU#572183 - ISC BIND 4 contains buffer overflow in nslookupComplain()
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0011
VU#868916 - ISC BIND 4 contains input validation error in
nslookupComplain()
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0013
VU#325431 - Queries to ISC BIND servers may disclose environment
variables
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2001-0012
For information on historical issues involving BIND vulnerabilities
and compromises, please visit
CERT Advisory CA-2000-20 Multiple Denial-of-Service Problems in ISC
BIND
http://www.cert.org/advisories/CA-2000-20.html
CERT Advisory CA-2000-03 Continuing Compromises of DNS servers
http://www.cert.org/advisories/CA-2000-03.html
CERT Advisory CA-1999-14 Multiple Vulnerabilities in BIND
http://www.cert.org/advisories/CA-1999-14.html
CERT Advisory CA-1998-05 Multiple Vulnerabilities in BIND
http://www.cert.org/advisories/CA-1998-05.html
CERT Advisory CA-1997-22 BIND - The Berkeley Internet Name Daemon
http://www.cert.org/advisories/CA-1997-22.html
CERT Summary CS-2000-02
http://www.cert.org/summaries/CS-2000-02.html
CERT Summary CS-2000-01
http://www.cert.org/summaries/CS-2000-01.html
CERT Summary CS-1999-04
http://www.cert.org/summaries/CS-99-04.html
CERT Summary CS-1998-07
http://www.cert.org/summaries/CS-98.07.html
CERT Summary CS-1998-06
http://www.cert.org/summaries/CS-98.06.html
CERT Summary CS-1998-05
http://www.cert.org/summaries/CS-98.05.html
CERT Summary CS-1998-04
http://www.cert.org/summaries/CS-98.04.html
For more information on transaction signatures, please visit
RFC 2535: Domain Name System Security Extensions
http://www.ietf.org/rfc/rfc2535.txt
RFC 2845: Secret Key Transaction Authentication for DNS (TSIG)
http://www.ietf.org/rfc/rfc2845.txt
Appendix A. - Vendor Information
This appendix contains information provided by vendors for this
advisory. When vendors report new information to the CERT/CC, we
update this section and note the changes in our revision history. If a
particular vendor is not listed below, we have not received their
comments.
Caldera Systems
OpenLinux 2.3, eServer 2.3.1 and eDesktop 2.4 are all vulnerable.
Update packages will be provided at
ftp://ftp.calderasystems.com/pub/updates/OpenLinux/2.3
ftp://ftp.calderasystems.com/pub/updates/OpenLinux/2.3
ftp://ftp.calderasystems.com/pub/updates/eDesktop/2.4
Compaq Computer Corporation
COMPAQ COMPUTER CORPORATION
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VU#325431 INFOLEAK
-
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Compaq Tru64 UNIX V5.1 and V5.0 *evaluation incomplete
Compaq Tru64 UNIX V4.0D/F/G *evaluation incomplete
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VU#572183 - buffer overflow in nslookupComplain()
VU#868916 - input validation error in nslookupComplain()
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Compaq Tru64 UNIX V5.1 and V5.0 - Not Vulnerable
Compaq Tru64 UNIX V4.0D/F/G - *evaluation incomplete.
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VU#196945 - BIND 8 contains buffer overflow in transaction signature handling
code
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Compaq Tru64 UNIX V5.1 and V5.0 - *evaluation incomplete
Compaq Tru64 UNIX V4.0D/F/G - Not Vulnerable
* At the time of writing this document, the problems identified are
currently still under evaluation by engineering. Compaq will provide
notice of the completion/availability of the patches through AES
services (DIA, DSNlink FLASH), the ** Security mailing list, and be
available from your normal Compaq Support channel.
**You may subscribe to the Security mailing list at:
http://www.support.compaq.com/patches/mailing-list.shtml
COMPAQ COMPUTER CORPORATION
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FreeBSD, Inc.
No supported version of FreeBSD contains BIND 4.x, so this does not
affect us. We current ship betas of 8.2.3 in the FreeBSD 4.x release
branch, and will be upgrading to 8.2.3 once it is released.
Hewlett-Packard Company
None of the Bind versions of HP-UX is vulnerable to VU#196945 -
problem of buffer overflow in TSIG handling code.
HP's Bind 8.1.2 is vulnerable to VU#325183 (infoleak problem). Bind
4.9.7 is vulnerable to both VU#572183 (infoleak problem) and VU#325183
(nslookupComplain() buffer overflow).
Fixes are in process.
IBM Corporation
VU#325431 - Queries to ISC BIND servers may disclose environment
variables
IBM's AIX operating system may be vulnerable to this "inverse query"
exploitation. We are working to understand the technical nature of
this exploit; when done, we expect to verify AIX's vulnerability. We
will provide updates to this page as we progress [in] studying this
exploit.
VU#572183 - ISC BIND 4 contains buffer overflow in nslookupComplain()
IBM's AIX operating system is vulnerable to this potential exploit in
named4. We are working to fix this quickly and we intend to post an
emergency fix ASAP.
VU#868916 - ISC BIND 4 contains input validation error in
nslookupComplain()
IBM's AIX operating system is vulnerable to this potential exploit,
and is working quickly toward a fix.
Sun Microsystems, Inc.
Solaris(tm) versions 2.4, 2.5, 2.5.1 and 2.6 contain revisions of BIND
4
Solaris(tm) versions 7 and 8 contain BIND 8.1.2
Sun is working to address the issues in VU#868916, VU#572183 and
VU#325431 and will be issuing a Sun Security Bulletin when further
information is available.
VU#196945 is not present in currently supported versions of Solaris.
_________________________________________________________________
The CERT/CC thanks the COVERT Labs at PGP Security for discovering and
analyzing three of these vulnerabilities (VU#196945, VU#572183, and
VU#868916) and Claudio Musmarra for discovering the infoleak
vulnerability (VU#325431). We also thank the Internet Software
Consortium for providing patches to fix the vulnerabilities.
_________________________________________________________________
This document was written by Jeffrey P. Lanza, Cory Cohen, Ian Finlay,
and Shawn Hernan.
______________________________________________________________________
This document is available from:
http://www.cert.org/advisories/CA-2001-02.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 personnel answer the hotline 08:00-20:00 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
http://www.cert.org/CERT_PGP.key
If you prefer to use DES, please call the CERT hotline for more
information.
Getting security information
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our web site
http://www.cert.org/
To subscribe to the CERT mailing list for advisories and bulletins,
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______________________________________________________________________
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