PHP 8.3 is fixed upstream in 8.3.36. Active support already ended on 31 December 2025, and security support continues until 31 December 2027. Builds below 8.3.36 are vulnerable if they are unmodified upstream code.
Lifecycle
PHP 8.3 has security support until 31 December 2027. The reference point from php.net is 8.3.36 is the fix. End-of-life status and a vendor backport are different facts. A branch can be unsupported by the PHP project and still have a distribution build that includes these two fixes.
What is confirmed about exposure
The defects are in the PHP runtime, so a PHP 8.3 process that serves HTTP is in the population PHP told users to update. mod_php is the highest-risk integration. PHP-FPM is not excluded. An application update does not change this runtime.
Upstream options
Install the fixed upstream release named above, from php.net or the Windows builds linked from the release announcement.
Vendor packages
Ubuntu 24.04 is the case that breaks a naive version check. Ubuntu lists php8.3 fixed in 8.3.6-0ubuntu0.24.04.13. The upstream string remains 8.3.6, which is older than 8.3.36, and Ubuntu still calls that package the fix. AlmaLinux lists php-8.3.33-1.module_el9.8.0+328+1fdeb728.alma.1 on AlmaLinux 9 and php-8.3.33-1.el10_2.alma.1 on AlmaLinux 10. Those are backports, not 8.3.36.
Nginx, Apache, and PHP-FPM
Nginx and Apache only route the request. On PHP 8.3, identify whether the vhost uses PHP-FPM, mod_php, or CGI. mod_php remains the highest-risk SAPI in PHP’s advisory regardless of how old the branch is. PHP-FPM on 8.3 is still in scope for CVE-2026-109619’s session path. Restart the daemon that loaded this branch after any package change. A host with PHP 8.3 and a newer PHP side by side is only fixed for the vhost you actually updated.
Remediation paths
If you built PHP from php.net, install 8.3.36. If you use Ubuntu 24.04 or AlmaLinux packages, compare the package revision with the vendor notice and restart PHP-FPM. Do not downgrade a working vendor backport just to make php -v print 8.3.36.
Temporary settings from the PHP advisory remain available and remain incomplete. See the mitigations page.
Production precautions
Snapshot or otherwise preserve the current packages before you change a production PHP 8.3 host. Expect a restart of php-fpm or Apache to drop active requests. If an extension fails to load, roll back and treat that as a compatibility problem, not as a reason to skip the CVE.
Validation
Query the binary the vhost uses after the restart. On backport-style packages, compare the package version rather than waiting for php -v to print a new upstream number. Check one authenticated and one anonymous application route you already know how to judge.
When to involve a specialist
Involve a specialist when PHP 8.3 is tied to a custom extension, a control-panel build, or a release process that cannot take the upstream tag directly. That is the normal case for this branch, not an edge case.
Questions
Is the last upstream PHP 8.3 release a PHP2Shell fix?
PHP 8.3 is fixed upstream in 8.3.36. Active support already ended on 31 December 2025, and security support continues until 31 December 2027. Builds below 8.3.36 are vulnerable if they are unmodified upstream code.
Can you help if we cannot upgrade this week?
Yes. The engagement can cover a vendor package check, exposure reduction, or a migration plan. It will not pretend a missing patch exists.