No choice but to turn off my Wordpress sites overnight. Living in UTC+x, it's practically a guarantee that the patch fixing this Severity 10 vulnerability will come through in the wee hours of the morning. Not taking the chance that some bot will rip through every Wordpress site as soon as the proofs of concept are let loose.

@futzle doing the rounds: A possible temp fix is to turn off session.upload_progress.enabled, i.e. add to your php.ini file and reload fpm:
session.upload_progress.enabled = Off
https://discourse.roots.io/t/upgrading-php-on-trellis-servers-for-the-oct-21-security-release/30439/2
Upgrading PHP on Trellis servers for the Oct 21 security release