Vulnerability Note VU#854315

ISC DHCPD contains format string vulnerability when logging DNS-update requests

Original Release date: 08 May 2002 | Last revised: 13 Jan 2003


The DHCP daemon (DHCPD) is a server that is used to allocate network addresses and assign configuration parameters to dynamically configured hosts. A format string vulnerability may permit an intruder to execute code with the privileges of the DHCP daemon (typically root).


The Internet Software Consortium (ISC) produces a DHCP server. DHCPD listens for requests from client machines connecting to the network. Versions 3 to 3.0.1rc8 inclusive of DHCPD contain an option (NSUPDATE) that is compiled in by default. NSUPDATE allows the DHCP server to send an update to the DNS server after processing a DHCP request. The DNS server responds by sending a message back to the DHCP server. The response from the DNS server can contain user-supplied data. When this message is received, the DHCP server logs the transaction. A format string vulnerability exists in the DHCPD code that logs the transaction. This vulnerability may permit an attacker to execute code with the privileges of the DHCP daemon.


A remote attacker can execute arbitrary code on the vulnerable host with the privileges of the DHCP server (DHCPD), typically root.


Obtain a patch from vendor.

If you cannot upgrade, apply the following patch.

--- common/print.c Tue Apr 9 13:41:17 2002
+++ common/print.c.patched Tue Apr 9 13:41:56 2002
@@ -1366,8 +1366,8 @@
*s++ = '.';
*s++ = 0;
if (errorp)
- log_error (obuf);
+ log_error ("%s",obuf);
- log_info (obuf);
+ log_info ("%s",obuf);
#endif /* NSUPDATE */

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
AlcatelAffected07 May 200229 May 2002
ConectivaAffected-13 May 2002
FreeBSDAffected06 May 200207 May 2002
ISCAffected-08 May 2002
NetBSDAffected06 May 200208 May 2002
Apple Computer Inc.Not Affected06 May 200214 May 2002
Cray Inc.Not Affected06 May 200213 May 2002
F5 NetworksNot Affected07 May 200208 May 2002
Fujitsu LimitedNot Affected06 May 200214 May 2002
Hewlett-Packard CompanyNot Affected06 May 200208 May 2002
IBMNot Affected06 May 200207 May 2002
Lotus Development CorporationNot Affected07 May 200208 May 2002
Microsoft CorporationNot Affected07 May 200208 May 2002
NEC CorporationNot Affected06 May 200214 May 2002
Nortel NetworksNot Affected07 May 200209 May 2002
If you are a vendor and your product is affected, let us know.View More »

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



The CERT Coordination Center acknowledges Next Generation Security Technologies as the discoverer of this vulnerability and thanks them and The Internet Software Consortium (ISC) for their cooperation, reporting and analysis of this vulnerability.

This document was written by Ian A. Finlay.

Other Information

  • CVE IDs: CAN-2002-0702
  • CERT Advisory: CA-2002-12
  • Date Public: 08 May 2002
  • Date First Published: 08 May 2002
  • Date Last Updated: 13 Jan 2003
  • Severity Metric: 46.17
  • Document Revision: 47


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