I am curious about that, too

Here was a PoC: https://jackalsyn.com/posts/php-up-2026.html

But it was withdrawn; now it says that it (CVE-2026-109618) is not an RCE and not even a CVE, apparently an addref call prevents the use-after-free. CVE-2026-109619 is still a memory safe bug, but they have no RCE for that one