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Internet Security Systems Security Alert
January 29, 2001

Remote Vulnerabilities in BIND versions 4 and 8

Synopsis:

ISS X-Force is aware of several vulnerabilities in current versions of
Internet Software Consortiums Berkeley Internet Name Domain (BIND). There
is a buffer overflow present in BIND version 8 that an attacker could use
to remotely execute arbitrary code. Version 4 of BIND contains three
vulnerabilities, a buffer overflow and a format string vulnerability, both
of which allow a remote attacker to execute arbitrary code, and a
vulnerability which can expose the environment variables of the BIND
server. BIND is the most popular implementation of the Domain Name Service
(DNS) protocol. DNS is the Internet protocol that converts host and domain
names into their corresponding IP addresses and vice-versa.  

Description:

ISC BIND 8 Buffer Overflow in Transaction Signature (TSIG) Handling Code:
BIND 8 contains a vulnerability that may allow a remote attacker to
compromise any server with a vulnerable version of BIND installed.  The
vulnerability is present in Transaction Signatures (TSIG) functionality.
Most current versions up to version 9.x are vulnerable.  It is not
necessary for the remote attacker to control an authoritative DNS server
to the target to exploit this vulnerability.  Both recursive and
non-recursive servers are vulnerable.

ISC BIND 4 Buffer Overflow in nslookupComplain():
A vulnerability exists in BIND 4 which under very specific circumstances
may allow remote attackers to compromise servers running vulnerable
versions of BIND 4.  A buffer overflow condition in the nslookupComplain()
function may be exploited to grant access to remote users.  The attacker
must have control of the targets authoritative nameserver to successfully
exploit this vulnerability.

ISC BIND 4 Input Validation Error in nslookupComplain():
The second vulnerability present in BIND 4 is present in the
nslookupComplain() function as well.  A user-supplied format string may be
manipulated to run arbitrary code.  The attacker must have control of the
targets authoritative nameserver to successfully exploit this
vulnerability.

ISC BIND 4 Exposure of Environment Variables:
This vulnerability may allow a remote attacker to expose variables within
the BIND server. By sending a malformed query to vulnerable BIND servers,
a remote attacker can gain access to the program stack.

Additional limitations to successful exploitation of this vulnerability
include the use of a limited character set when constructing the overflow
string, as well as dynamic conditions such as the layout and allocation of
memory for the BIND process.

Affected Systems:

ISC BIND version 8:
8.2, 8.2.1
8.2.2 through 8.2.2-P7
8.2.3-T1A through 8.2.3-T9B
ISC Bind version 4:
4.9.3 through 4.9.7

Recommendations:

It is recommended that all DNS administrators using BIND 4.9.x upgrade to
BIND 4.9.8 and those using BIND 8.2.x upgrade to BIND 8.2.3. These
upgrades may be found at:  ftp://ftp.isc.org/isc/BIND/src/.

DNS administrators should take precautions to limit the affects of
permissions on their DNS server installations.  The DNS server should
never be executed with super-user privileges, and should also be sandboxed
under a chroot environment.

Please refer to the following URL for information on the use of  chroot
in order to provide an additional layer of security for exposed services:
http://securityportal.com/cover/coverstory20001002.html

ISS SAFEsuite intrusion detection system, RealSecure, and network
security assessment product, Internet Scanner, will have signatures
available to detect these vulnerabilities in the next X-Press Updates.

Credits and References:

CERT Advisory CA-201-02 Multiple Vulnerabities in BIND
http://www.cert.org/advisories/CA-2001-02.html
Network Associates Advisory
http://www.pgp.com/research/covert/advisories.asp
Internet Software Consortium
http://www.isc.org/products/BIND/bind-security.html
New BIND 4 and BIND 8 releases
ftp://ftp.isc.org/isc/bind/src/
BIND 9.1
ftp://ftp.isc.org/isc/bind9/


About Internet Security Systems (ISS) 

Internet Security Systems (ISS) is a leading global provider of security
management solutions for the Internet. By providing industry-leading
SAFEsuite security software, remote managed security services, and
strategic consulting and education offerings, ISS is a trusted security
provider to its customers, protecting digital assets and ensuring safe and
uninterrupted e-business. ISS' security management solutions protect more
than 5,500 customers worldwide including 21 of the 25 largest U.S.
commercial banks, 10 of the largest telecommunications companies and over
35 government agencies. Founded in 1994, ISS is headquartered in Atlanta,
GA, with additional offices throughout North America and international
operations in Asia, Australia, Europe, Latin America and the Middle East.
For more information, visit the Internet Security Systems web site at
www.iss.net or call 888-901-7477.

Copyright (c) 2001 Internet Security Systems, Inc.

Permission is hereby granted for the redistribution of this Alert
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of the X-Force. If you wish to reprint the whole or any part of this Alert
in any other medium excluding electronic medium, please e-mail
xforce@iss.net for permission.

Disclaimer

The information within this paper may change without notice. Use of this
information constitutes acceptance for use in an AS IS condition. There
are NO warranties with regard to this information. In no event shall the
author be liable for any damages whatsoever arising out of or in
connection with the use or spread of this information. Any use of this
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Please send suggestions, updates, and comments to: X-Force
mailto:xforce@iss.net of Internet Security Systems, Inc.

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