Errata patches for the kernel have been released for OpenBSD 6.5 and 6.6. A local user could cause the system to hang by reading specific registers when Intel Gen8/Gen9 graphics hardware is in a low power state.
A local user could perform writes to memory that should be blocked with Intel Gen9 graphics hardware. Binary updates for the amd64 and i386 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 As these affect the kernel, a reboot will be needed after patching.