In FreeBSD 12.1-STABLE before r356908, 12.1-RELEASE before p5, 11.3-STABLE before r356908, and 11.3-RELEASE before p9, a race condition in the cryptodev module permitted a data structure in the kernel to be used after it was freed, allowing an unprivileged process can overwrite arbitrary kernel memory.
https://security.netapp.com/advisory/ntap-20200518-0005/
https://security.FreeBSD.org/advisories/FreeBSD-SA-20:15.cryptodev.asc