Errata patches for dhcpd have been released for OpenBSD 6.4 and 6.5. dhcpd leaks 4 bytes of stack to the network.
Binary updates for the amd64, i386, and arm64 platforms are available via the syspatch utility. Source code patches can be found on the respective errata page: https://www.openbsd.org/errata64.html https://www.openbsd.org/errata65.html After patching, restart the dhcpd service.