Errata patches for libc have been released for OpenBSD 6.6 and 6.7. libc's resolver could get into a corrupted state.
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/errata66.html https://www.openbsd.org/errata67.html