Errata patches for unbound have been released for OpenBSD 6.2. A flaw was found in the way unbound validated wildcard-synthesized NSEC records. An improperly validated wildcard NSEC record could be used to prove the non-existence (NXDOMAIN answer) of an existing wildcard record, or trick unbound into accepting a NODATA proof.
For details, see https://unbound.net/downloads/CVE-2017-15105.txt 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/errata62.html After patching, restart the unbound service.