CVE-2018-5733: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 20.2% chance of exploitation in the next 30 days.

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. Affects ISC DHCP 4.1.0 -> 4.1-ESV-R15, 4.2.0 -> 4.2.8, 4.3.0 -> 4.3.6, 4.4.0.

Affected products

• Canonical Ubuntu Linux: version 14.04 only; version 16.04 only; version 17.10 only
• Debian Debian Linux: version 7.0 only; version 8.0 only; version 9.0 only
• ISC Dhcp: from 4.2.0, up to and including 4.2.8; from 4.3.0, up to and including 4.3.6; version 4.1-esv only; version 4.1.0 only; version 4.4.0 only
• Red Hat Enterprise Linux Desktop: version 6.0 only; version 7.0 only
• Red Hat Enterprise Linux Server: version 6.0 only; version 7.0 only
• Red Hat Enterprise Linux Server Aus: version 7.4 only; version 7.6 only
• Red Hat Enterprise Linux Server Eus: version 7.4 only; version 7.5 only; version 7.6 only
• Red Hat Enterprise Linux Workstation: version 6.0 only; version 7.0 only

Published 2019-01-16. Last modified 2026-06-17.