TL;DR On October 21, 2026, PHP released emergency patches for two critical flaws known together as PHP2Shell (CVE-2026-109618 and CVE-2026-109619). An attacker with no credentials can use them to run code on a PHP web server, in some cases with a single HTTP request. Upgrade to PHP 8.2.35, 8.3.36, 8.4.27 or 8.5.12 now.