2026-11-02 21:38 UTC
you do know you can just put a firewall rule in to prevent any IP options from hitting the server
The rule (matches header length > 20 bytes, i.e. IHL 6–15):
iptables -I INPUT 1 -m u32 --u32 "0>>24&0x0F=6:15" -m comment --comment ipopts-stopgap -j DROP
ufw: add -A ufw-before-input -m u32 --u32 "0>>24&0x0F=6:15" -j DROP to /etc/ufw/before.rules, above the RELATED,ESTABLISHED accept line. Then run ufw reload.
csf: put the iptables line in /usr/local/csf/bin/csfpre.sh so it survives csf restarts.
Docker hosts: use -t raw -I PREROUTING instead, so container traffic is covered too.
Test: run ping -R at the box and watch the counter go up in iptables -L INPUT -v -n. Note that many networks drop option packets in transit, so test from the same LAN or a local netns.
its a stopgap. not a fix. but you don't have to take all your servers offline .....
just put the block in and wait for the patch
Replies (2)
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@MonkderVierte@lemmy.zip 2026-11-03 10:47
Do you also have a nftables rule? (Who even uses ufw on server?)
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@protogen420@lemmy.blahaj.zone 2026-11-03 12:16
ok gpt