I know it's customary for HN to edit titles to remove extraneous information, but removing "Linux" here really takes away something useful and relevant. This is a Linux vulnerability. If you're running *BSD or Mac or Windows, not affected.
"Why it's urgent: the bug sits in code every Linux server runs when it accepts an IPv4 TCP connection, before any application sees the connection. Anthropic, whose researcher reported it, says its Claude model wrote a working proof-of-concept exploit that runs commands as root on "Linux servers with a multipath TCP listener," with no credentials. Go programs open those listeners by default, per the Go Security Team. See the timeline."
I don't know of any Linux boxes running a multipath TCP listener in my care and I have quite a few. MP generally implies a router of some sort and the intersections in a Venn diagram continue to get smaller ...
This is still an issue and must be patched but I think it will be rare, very rare.
1: https://groups.google.com/g/golang-announce/c/PCoQcdxoScw
MPTCP doesn’t use any specific ports. It’s an OSI layer higher than that. It’s part of the TCP protocol itself. So if your firewall routes TCP traffic of a specific port (eg HTTP) already then it’ll route MPTCP along with it too.
sudo ss -lnp -A mptcp