FreeBSD Security Advisory – The SIOCSIFINFO_IN6 ioctl is missing a necessary permissions check. Local users, including non-root users and users inside jails, can set some IPv6 interface properties. These include changing the link MTU and disabling interfaces entirely.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/78264/FreeBSD-SA-09-10.ipv6.txt
Source: https://packetstormsecurity.com/files/78264/FreeBSD-Security-Advisory-IPv6-Permission-Check.html