Errata patches for the kernel have been released for OpenBSD 6.5 and 6.6. ARM64 CPUs speculatively execute instructions after ERET.
Binary updates for the arm64 platform 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.
