Red Hat also claims that netfilter is not enough: https://access.redhat.com/security/vulnerabilities/RHSB-2026...
> The following nftables table drops incoming IPv4 TCP packets that contain IP options, which reduces exposure to this vulnerability but cannot fully prevent it.
I know things like eBPF can technically bypass netfilter if someone tries hard enough, but I'm not sure if they're referring to any other ways to exploit this that a netfilter rule can't catch.
Firejail by default also allows unprivileged users to completely bypass any netfilter rules from the main network namespace... so if the user has that installed (even if they don't use it), it's something to keep in mind.
A system running multiple network namespaces might not have the same mitigations applied inside all of them, so be sure to check all of those, except there's no great way of even finding all the different namespaces running on a Linux system for some reason (please prove me wrong if something exists! lsns is not enough).
But yes I agree it seems strange that most posts/articles/etc. are not prominently giving out mitigation strategies.