In FreeBSD before 11.0-STABLE, 11.0-RELEASE-p10, 10.3-STABLE, and 10.3-RELEASE-p19, ipfilter using "keep state" or "keep frags" options can cause a kernel panic when fed specially crafted packet fragments due to incorrect memory handling.
https://www.freebsd.org/security/advisories/FreeBSD-SA-17:04.ipfilter.asc