setup-php is a GitHub action to set up PHP with extensions, php.ini configuration, coverage drivers, and tools. From 2.25.0 prior to 2.37.1, shivammathur/setup-php resolves the PHP version from repository-controlled files such as .php-version, composer.lock through platform-overrides.php, and composer.json through config.platform.php, and insufficiently constrains those values before incorporating them into generated shell or PowerShell setup scripts, allowing command injection on a GitHub Actions runner when workflows such as pull_request_target check out attacker-controlled contents before invoking setup-php. This issue is fixed in version 2.37.1.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:LI:LA:L5.6/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:LInjection