Fragmentation is a nightmare in a nightmare: we also discovered that IPv6 fragments reassembly (as implemented by major operating systems) is still plagued by the problem of overlapping fragments. Potentially, you can still bypass IDS/IPS using the same techniques from IPv4...

Shameless plug: we will present these results at ESORICS 2023 :-)

IPv4 fragmentation was even worse since any device in the middle could fragment packets. IPv6 atleast limits it to the client/host. I still think they should have designed IPv6 to include L4 info in each fragment to avoid having to reassemble to get that data.