CERT: DHCP bug could give attackers control

By Sam Costello, IDG News Service |  Security

A vulnerability in the DHCP (Dynamic Host Configuration Protocol) server provided by the Internet Software Consortium (ISC) could allow attackers to take over affected servers, according to a security alert released by the CERT Coordination Center Wednesday.

The DHCP server, or daemon, provided by ISC allows administrators to centralize the management and assigning of IP (Internet Protocol) addresses to devices. The ISC's DHCP implementation installs a component called NSUpdate by default that allows the DHCP server to send information about hosts on the network to a DNS (domain name server), CERT/CC said. When the DNS server receives that information, it responds to the DHCP server acknowledging the transaction. When the DHCP server receives the message, it logs the transaction, CERT/CC said.

The vulnerability in the DHCP server comes in the code that logs the communication from the DNS server, CERT/CC said. The bug affects versions 3 to 3.0.1 rc8 of ISC's DHCP implementation, CERT/CC said.

An attacker who successfully exploited the hole would be able to run code with the privileges of the DHCP server, which is often root, CERT/CC's alert said. Root privilege is the highest privilege level and allows a user complete control over a system.

To address the flaw, CERT/CC recommends that users apply vendor-supplied patches, disable the DHCP service if it is not needed or apply the ingress filtering techniques detailed in its alert.

Products from Hewlett-Packard Co., IBM Corp., Lotus Software Group, Microsoft Corp., as well as the NetBSD and FreeBSD operating systems, are not affected, CERT/CC said.

The CERT/Coordination Center is a government-funded security research and development body located at Carnegie Mellon University in Pittsburgh.

More information about the vulnerability can be found in CERT/CC's alert, located at http://www.cert.org/advisories/CA-2002-12.html.

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