OpenBSD 5.8 and 5.9 allows certain local users with kern.usermount privileges to cause a denial of service (kernel panic) by mounting a tmpfs with a VNOVAL in the (1) username, (2) groupname, or (3) device name of the root node.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 13.8%