Errata patches for ld.so have been released for OpenBSD 6.5 and 6.6. ld.so may fail to remove the LD_LIBRARY_PATH environment variable for set-user-ID and set-group-ID executables in low memory conditions.
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/errata65.html https://www.openbsd.org/errata66.html