-----BEGIN PGP SIGNED MESSAGE----- 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, inclusive. * For detailed vendor status information, see http://www.kb.cert.org/vuls/id/284857#systems 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. 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. 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. 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/. 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 Xerox is aware of this vulnerability and is currently assessing all products. This statement will be updated as new information becomes available. _________________________________________________________________ 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: http://www.cert.org/advisories/CA-2003-01.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 http://www.cert.org/CERT_PGP.key 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 http://www.cert.org/ To subscribe to the CERT mailing list for advisories and bulletins, send email to majordomo@cert.org. Please include in the body of your message subscribe cert-advisory * "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 2003 Carnegie Mellon University. Revision History January 15, 2003: Initial release -----BEGIN PGP SIGNATURE----- Version: PGP 6.5.8 iQCVAwUBPiW+92jtSoHZUTs5AQEncQQAsuYjk8gUeHb3Ch+dflrvDucfjy+EHy6E TAeG+Hc9VZjhzxnK8Fmk9bNW5HP9LOlzJG0xSlEOtfbbfUEikq5onPwIEz/w5CfG d9jse1JM7q+Di6C9NmRZG42CP4Y2a9YSHK2RT+o6B6kurg0DfQyir0AzrIvUReMC Pbev3WAZs8s= =yhDV -----END PGP SIGNATURE-----