The root cause was a Linux kernel bug (a netfilter xtables typo), not a Tailscale bug, it was fixed upstream in kernels 6.11.6 and 6.6.59, and distros shipped the fix (NixOS, Arch 6.11.4-arch2-1, Ubuntu, Fedora). Upgrade your kernel to a fixed release. As a workaround on an affected kernel, force nf…