From the little info one can see here, it looks like this is a PHP script causing a memory corruption. So you probably need to be able to run PHP code to exploit it.

That's... not a particularly unusual issue. PHP has a large codebase, releases with plenty of fixed crashes come out regularly. It becomes critical if there's a remote path to exploitation.

I see no indication that this is a "critical" PHP flaw. And the Reply from the person who found it seems to confirm that. ("I keep getting asked about mitigations, here's the mitigation: don't worry about it kitten")

I read their quip about mitigation as more of a defeatist "this is fine" meme than actual advice that it's a nothingburger, but I'm pretty cynical on PHP as a whole. We'll have to wait and see if today's a hat trick day or just a double header.