ugh. the patch is massive the bug is based on causing an OOM condition and no-one ever accused the php interpreter of being neatly and elegantly architected, so the fix touches everything the bugs go back many years but backporting the fix to all those versions is wildly impractical
the exploit was developed with AI assistance but it was based on existing human research, including by my old nemesis Stefan Esser. I don't remember why he's my nemesis, I assume we got into a stupid twitter argument over nothing like 16 years ago