FreeBSD Security Advisory – FreeBSD-SA-19:06.pf

FreeBSD Security Advisory – States in pf(4) let ICMP and ICMP6 packets pass if they have a packet in their payload matching an existing condition. pf(4) does not check if the outer ICMP or ICMP6 packet has the same destination IP as the source IP of the inner protocol packet. A maliciously crafted ICMP/ICMP6 packet could bypass the packet filter rules and be passed to a host that would otherwise be unavailable.

Link: https://packetstormsecurity.com/files/152934/FreeBSD-SA-19.06.pf.txt