PHP Vulnerabilities CVE-2026-109618 and CVE-2026-109619

Update timeline

1. investigating Oct 21, 2026, 02:03 PM UTC

   Pantheon is actively mitigating against the PHP security vulnerabilities announced at 14:00 UTC today. PHP environments are being patched to the following versions: 8.5.12 8.4.27 8.3.36 8.2.35 Additionally, we are patching the following heirloom PHP branches via our LTS vendor: 8.1.x 8.0.x 7.4.x 7.3.x 7.2.x 7.1.x 7.0.x 5.6.x Finally, in preparation for this event, we pre-emptively deployed configuration changes to the runtime environment to mitigate potential attack vectors, and have implemented network-level mitigations to deflect attempted exploit payloads across the platform. No action is required from customers, as all available versions of PHP on Pantheon receive security updates through our LTS vendor. However, we continue to recommend that customers running on older versions of PHP that have reached End of Sale update to a version fully supported by the PHP community in order to minimize their overall risk. To pin your version of PHP to a different version, see https://docs.pantheon.io/guides/php/php-versions. We will update this post as patching progresses and as we learn more about the vulnerability.

2. investigating Oct 21, 2026, 02:36 PM UTC

   Updated PHP versions addressing CVE-2026-109618 and CVE-2026-109619 are now available, and we are beginning the process of rolling them out across our infrastructure. No action is required from customers. We will continue to update this post as the rollout progresses.