Introduction: Persistent RCE Vulnerabilities in PHP Servers Post-Patching

Despite the release of patches for critical remote-code-execution (RCE) vulnerabilities CVE-2026-109618 and CVE-2026-109619 , PHP servers remain susceptible to exploitation due to a fundamental oversight in the patching process. As highlighted in the October 23 advisory by Google and Mandiant, installing patches does not inherently secure active PHP processes. The root cause lies in the persistence of pre-patch PHP worker processes in memory, which continue to execute requests using the vulnerable runtime version. These lingering processes function as exploitable entry points, enabling attackers to execute arbitrary code and compromise server integrity.

The vulnerability mechanism is technically precise: upon patch deployment, the operating system or package manager updates the PHP runtime files on disk. However, active worker processes spawned prior to patching remain resident in memory , unaffected by the updated files.…