It's so much worse than this, and there is a staggering amount of misinformation running rampant about this bug.
MPTCP is not a requirement, it can be exploited merely by sending specially crafted TCP packets with (any) IP options set. No special MPTCP support, web servers or any specific software listeners are even necessary at all to trigger it, just send the packets and boom.
I think the reason people assume MPTCP is a requirement is because that's what the PoC used... but MPTCP itself also doesn't even rely solely on IP options.
Ubuntu also does not even list a single mitigation strategy... at least RHEL did.
And like I said, any normal TCP packet that contains IP (not TCP) options can trigger the bug. I cannot emphasize enough how important and absolutely ridiculous this is.
Like the post says, this is big enough to get a massive amount of people to completely stop trusting Ubuntu entirely and jump ship.
For Ubuntu (which I don't use), you'd need a 3rd party updated kernel repo, to use a patched kernel from that.
It's not an instantaneous exploit, it takes a lot of iteration over the network. A lot of cloud network providers are mitigating it by dropping options at the border, but unless you test and confirm that, you should assume it's possible for a motivated-enough attacker to compromise your server.
I assume this is unrelated to the Ubuntu situation, but how does a grammar checker go down? We've been doing offline grammar checking since computers had 64K of RAM.
At one point that was less than $100 of RAM which isn't a big deal for the trade.
I should have asked what is it there in replacing yourself with a mishmash of external world.