Last updated 8 June 2026

Sending a maliciously crafted message to the kea-ctrl-agent, kea-dhcp-ddns, kea-dhcp4, or kea-dhcp6 daemons over any configured API socket or HA listener can cause the receiving daemon to exit with a stack overflow error. This issue affects Kea versions 2.6.0 through 2.6.4 and 3.0.0 through 3.0.2.

To trigger the issue, three configuration parameters must have specific settings: "hostname-char-set" must be left at the default setting, which is "[^A-Za-z0-9.-]"; "hostname-char-replacement" must be empty (the default); and "ddns-qualifying-suffix" must NOT be empty (the default is empty). DDNS updates do not need to be enabled for this issue to manifest. A client that sends certain option content would then cause kea-dhcp4 to exit unexpectedly. This issue affects Kea versions 3.0.1 through 3.0.1 and 3.1.1 through 3.1.2.

To trigger the issue, three configuration parameters must have specific settings: "hostname-char-set" must be left at the default setting, which is "[^A-Za-z0-9.-]"; "hostname-char-replacement" must be empty (the default); and "ddns-qualifying-suffix" must NOT be empty (the default is empty). DDNS updates do not need to be enabled for this issue to manifest. A client that sends certain option content would then cause kea-dhcp4 to exit unexpectedly. This issue affects Kea versions 3.0.1 through 3.0.1 and 3.1.1 through 3.1.2.

An invalid hostname option can trigger an assertion failure in the Kea DHCPv4 server process (kea-dhcp4), causing the server process to exit. Versions affected: 1.4.0 to 1.5.0, 1.6.0-beta1, and 1.6.0-beta2.