The follow nginx settings do seem to resolve the issue but I'd prefer to wait until the official fix is released 👨‍💻

fastcgi_buffering on;
fastcgi_buffer_size 128k;
fastcgi_buffers 8 16m;

Testing is now completed and all sites are now running under PHP 8.4.1

Whilst this attack continues, any hacking attempt originating from China will result in an automatic network range block on our external firewall for 48 hours. Currently 15,292,576 individual IP addresses have been blocked.