CERT-SEI

Buffer Overflows in ISC DCHPD Minires Library

Original release date: January 15, 2003
Last revised: March 26, 2003
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, inclusive.
  • For detailed vendor status information, see VU#284857

Overview

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 exploits.


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

http://www.kb.cert.org/vuls/id/284857#systems

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 comments.

Alcatel

Following CERT advisory CA-2003-01 on security vulnerabilities in the ISC DHCP implementation, Alcatel has conducted an immediate assessment to determine any impact this may have on our portfolio. A first analysis has shown that none of our products is impacted. The security of our customers' networks is of highest priority for Alcatel. Therefore we continue to test our product portfolio against potential ISC DHCP security vulnerabilities and will provide updates if necessary.

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 products.

Debian

Debian has updated their distribution with DSA 231.

For the stable distribution (woody) this problem has been fixed in version 3.0+3.0.1rc9-2.1.

The old stable distribution (potato) does not contain dhcp3 packages.

For the unstable distribution (sid) this problem has been fixed in version 3.0+3.0.1rc11-1.

Fujitsu

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

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: mailto:security-alert@hp.com

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.

Ingrian Networks

Ingrian Networks products are not vulnerable to VU#284857.

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 http://www.isc.org/products/DHCP/.

Microsoft Corporation

Microsoft products do not use the libraries in question. Microsoft products are not affected by this vulnerability.

MontaVista Software

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

NEC Inc.

[Server Products]
* EWS/UP 48 Series operating system
- is NOT vulnerable.

NetBSD

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

NetScreen is not vulnerable to this issue.

OpenBSD

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 suite.

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.

http://rhn.redhat.com/errata/RHSA-2003-011.html

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

A response to this advisory is available from our web site:  http://www.xerox.com/security.


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.

Copyright 2003 Carnegie Mellon University.

Revision History

Jan 15, 2003:  Initial release
Jan 20, 2003:  Added vendor statement for Debian
Jan 28, 2003:  Added vendor statement for Microsoft Corporation
Mar 25, 2003:  Added vendor statement for Ingrian Networks
Mar 26, 2003:  Updated vendor statement for Xerox Corporation
Mar 26, 2003:  Added vendor statement for Alcatel