setsockopt(2) IPv6 sockets input validation error

From the FreeBSD Security Advisory:

A programming error in the handling of some IPv6 socket
options within the setsockopt(2) system call may result
in memory locations being accessed without proper
validation.
It may be possible for a local attacker to read portions
of kernel memory, resulting in disclosure of sensitive
information. A local attacker can cause a system
panic.