Remotely Exploitable Flaws Patched in DHCP

Updates released by the Internet Systems Consortium (ISC) for the Dynamic Host Configuration Protocol (DHCP) software patch two remotely exploitable vulnerabilities discovered by a researcher at Google.

Felix Wilhelm of the Google Security Team found that the DHCP Client (dhclient), which provides a means for configuring network interfaces, is affected by a buffer overflow vulnerability that allows a malicious server to cause the client to crash.

In some cases, exploitation of the flaw could also lead to remote code execution, ISC said in an advisory. The security hole is tracked as CVE-2018-5732 and rated high severity.

“Where they are present, operating system mitigation strategies such as address space layout randomization (ASLR) should make it difficult to leverage this vulnerability to achieve remote code execution but we can not rule it out as impossible. The safest course is to patch dhclient so that the buffer overflow cannot occur,” ISC said.

The second vulnerability, CVE-2018-5733, is a medium severity issue that can be exploited to exhaust the memory available to the DHCP daemon (dhcpd), resulting in a denial-of-service (DoS) condition to clients.

“A malicious client which is allowed to send very large amounts of traffic (billions of packets) to a DHCP server can eventually overflow a 32-bit reference counter, potentially causing dhcpd to crash,” ISC said.

The flaws affect DHCP versions 4.1.0 through 4.1-ESV-R15, 4.2.0 through 4.2.8, 4.3.0 through 4.3.6, and 4.4.0. Fixes are included in versions 4.1-ESV-R15-P1, 4.3.6-P1 and 4.4.1.

ISC said there was no evidence that the vulnerabilities had been exploited for malicious purposes.

The organization has also informed customers of a vulnerability affecting BIND Supported Preview Edition, which is a customer-only, non-public version of BIND. The flaw, tracked as CVE-2018-5734 and rated high severity, can lead to an assertion failure, which typically causes the software to crash.

Related: Google Finds Flaws in Dnsmasq Network Services Tool

Related: DNS Servers Crash Due to BIND Security Flaw