sys/kern/sysv_sem.c in OpenBSD through 7.9 has a use-after-free allowing local privilege escalation to root. This is a context switch use-after-free after tsleep in sys_semget().
https://openai.com/index/patch-the-planet/
https://github.com/openbsd/src/commit/1957873d2063db11dab780eca75b5e629d1e838d