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().
Exploitability
AV:LAC:HPR:NUI:NScope
S:UImpact
C:HI:HA:H7.4/CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HMemory Safety