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CA-2003-01 Buffer Overflows in ISC DHCPD Minires Library


CERT Advisory CA-2003-01 Buffer Overflows in ISC DHCPD Minires Library

Original release date: January 15, 2003
Last revised: --
Source: CERT/CC

A complete revision history can be found at the end of this file.

Systems Affected

* Systems running ISC DHCPD versions 3.0 through 3.0.1RC10,
* For detailed vendor status information, see


The Internet Software Consortium (ISC) has discovered several buffer
overflow vulnerabilities in their implementation of DHCP (ISC DHCPD).
These vulnerabilities may allow remote attackers to execute arbitrary
code on affected systems. At this time, we are not aware of any

I. Description

There are multiple remote buffer overflow vulnerabilities in the ISC
implementation of DHCP. As described in RFC 2131, "the Dynamic Host
Configuration Protocol (DHCP) provides a framework for passing
configuration information to hosts on a TCP/IP network." In addition to
supplying hosts with network configuration data, ISC DHCPD allows the
DHCP server to dynamically update a DNS server, eliminating the need
for manual updates to the name server configuration. Support for
dynamic DNS updates is provided by the NSUPDATE feature.

During an internal source code audit, developers from the ISC
discovered several vulnerabilities in the error handling routines of
the minires library, which is used by NSUPDATE to resolve hostnames.
These vulnerabilities are stack-based buffer overflows that may be
exploitable by sending a DHCP message containing a large hostname
value. Note: Although the minires library is derived from the BIND 8
resolver library, these vulnerabilities do not affect any current
versions of BIND.

The CERT/CC is tracking this issue as VU#284857. This reference number
corresponds to CVE candidate CAN-2003-0026.

II. Impact

Remote attackers may be able to execute arbitrary code with the
privileges of the user running ISC DHCPD.

III. Solution

Upgrade or apply a patch

The ISC has addressed these vulnerabilities in versions 3.0pl2 and
3.0.1RC11 of ISC DHCPD. If your software vendor supplies ISC DHCPD as
part of an operating system distribution, please see Appendix A for
vendor-specific patch information.

For a detailed list of vendors that have been notified of this issue by
the CERT/CC, please see

Disable dynamic DNS updates (NSUPDATE)

As an interim measure, the ISC recommends disabling the NSUPDATE
feature on affected DHCP servers.

Block external access to DHCP server ports

As an interim measure, it is possible to limit exposure to these
vulnerabilities by restricting external access to affected DHCP servers
on the following ports:

bootps 67/tcp # Bootstrap Protocol Server
bootps 67/udp # Bootstrap Protocol Server
bootpc 68/tcp # Bootstrap Protocol Client
bootpc 68/udp # Bootstrap Protocol Client

Disable the DHCP service

As a general rule, the CERT/CC recommends disabling any service or
capability that is not explicitly required. Depending on your network
configuration, you may not need to use DHCP.

Appendix A. - Vendor Information

This appendix contains information provided by vendors for this
advisory. As vendors report new information to the CERT/CC, we will
update this section and note the changes in our revision history. If a
particular vendor is not listed below, we have not received their

Apple Computer, Inc.

Mac OS X and Mac OS X Server do not contain the vulnerability described
in this notice.

Berkeley Software Design, Inc. (BSDI)

This vulnerability is addressed by the M431-001 and M500-004 patches
for the 4.3.1 and 5.0 versions of BSD/OS.

Cisco Systems

No Cisco products have been found to be affected by this vulnerability.

Several Cisco products do utilize the ISC DHCPD, however, no Cisco
products implement the ISC DHCPD NSUPDATE feature, nor do they include
the minires library.

Cray Inc.

Cray Inc. is not vulnerable as dhcpd is not supported on any of its


Fujitsu's UXP/V OS is not vulnerable because it does not support the

Hewlett-Packard Company

Source: Hewlett-Packard Company
Software Security Response Team

cross reference id: SSRT2423

HP-UX - not vulnerable
HP-MPE/ix - not vulnerable
HP Tru64 UNIX - not vulnerable
HP OpenVMS - not vulnerable
HP NonStop Servers - not vulnerable

To report potential security vulnerabilities in HP software,
send an E-mail message to:

Hitachi, Ltd.

We've checked up on our router (Hitachi,Ltd. GR2000 series) about
[VU#284857]. Our DHCP implementation is NOT vulnerable.

IBM Corporation

IBM's AIX does not ship with the ISC DHCP daemon. The issues discussed
in VU#284857 or any following advisories based on this vulnerability
note do not pertain to AIX.

Internet Software Consortium

We have a patched version of 3.0 available (3.0pl2) and a new release
candidate for the next bug-fix release (3.0.1RC11). Both of these new
releases are available from

MontaVista Software

None of MontaVista Software's Linux products are vulnerable to this

NEC Inc.

[Server Products]

* EWS/UP 48 Series operating system
- is NOT vulnerable.


Currently supported versions of NetBSD do not contain the error
handling routine vulnerabilities. Such vulnerabilities were fixed
prior to the release of NetBSD 1.5.

With respect to the patch to ns_name.c, we believe that this is good
defensive programming and have applied the patch to NetBSD-current.
However, all calls to ns_name_ntol in the NetBSD source base pass a
correct, constant, non-zero value as the datsiz parameter.

Therefore, NetBSD is not vulnerable.


NetScreen is not vulnerable to this issue.


OpenBSD's dhcp support is much modified, does not have that feature,
and therefore does not have that bug.

Openwall GNU/*/Linux

Openwall GNU/*/Linux is not vulnerable. We don't yet provide a DHCP

Red Hat Inc.

Red Hat distributes a vulnerable version of ISC DHCP in Red Hat Linux
8.0. Other distributions of Red Hat Linux are not vulnerable to these
issues. New DHCP packages are available along with our advisory at the
URL below. Users of the Red Hat Network can update their systems using
the 'up2date' tool.

Riverstone Networks

Riverstone Networks is not vulnerable to VU#284857.

Sun Microsystems, Inc.

Sun confirms that we are not vulnerable to the issues described in
VU#284857. Solaris does not ship the ISC DHCPD and does not use any of
the ISC DHCPD source in its version of DHCPD.

SuSE Linux AG

We are preparing updates, that will be released soon.


Xerox is aware of this vulnerability and is currently assessing all
products. This statement will be updated as new information becomes

The CERT Coordination Center thanks David Hankins of the Internet
Software Consortium for notifying us about this problem and for helping
us to construct this document. We also thank Jacques A. Vidrine for
drawing attention to this issue.

Author: This document was written by Jeffrey P. Lanza.

This document is available from:

CERT/CC Contact Information

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Fax: +1 412-268-6989
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Software Engineering Institute
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Pittsburgh PA 15213-3890

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Revision History
January 15, 2003: Initial release

Version: PGP 6.5.8


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