CVE-2026-46420: Setup PHP Command Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pqwm-q9pv-ph8r",
  "modified" : "2026-05-20T15:31:52Z",
  "published" : "2026-05-20T15:31:52Z",
  "aliases" : [ "CVE-2026-46420" ],
  "summary" : "Setup PHP: Command Injection in Repository-Derived PHP Version Resolution",
  "details" : "### Summary\n\nA command injection vulnerability was identified in `shivammathur/setup-php` when the action resolves the PHP version from repository-controlled files and uses that value while generating the platform setup script.\n\nIn affected versions, `setup-php` may read the PHP version from:\n\n- `.php-version`\n- `composer.lock` via `platform-overrides.php`\n- `composer.json` via `config.platform.php`\n\nIf an attacker can influence one of these files and the workflow executes `setup-php` in a trusted context, they may be able to execute commands on the GitHub Actions runner.\n\n### Impact\n\nThis issue is exploitable when `setup-php` is run after checking out attacker-controlled repository contents and resolves the PHP version from repository files.\n\nThe most significant example is a privileged workflow such as `pull_request_target` that checks out untrusted pull request code before invoking `setup-php`. Similar risk can also arise in other workflows that operate on attacker-controlled refs, branches, or repository contents in a trusted context.\n\nThis is not a separate security boundary when an attacker can already modify the workflow definition itself or directly control the `php-version` workflow input, since that level of access already permits arbitrary command execution in GitHub Actions.\n\n### Technical details\n\nIn affected versions, repository-derived PHP version values were insufficiently constrained before being incorporated into the generated shell or PowerShell setup script executed by the action. This could allow attacker-controlled values from supported repository files to influence script execution in trusted workflow contexts.\n\n### Remediation\n\nIf you are using `shivammathur/setup-php@v2`, no action is needed on your end. Users who pin the setup-php release version or release version SHA should upgrade to a patched version.\n\nThe fix validates PHP version inputs, constrains manifest-derived versions, hardens script generation at the execution, and includes additional checks in related input-handling paths.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "GitHub Actions",
      "name" : "shivammathur/setup-php"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.25.0"
      }, {
        "fixed" : "2.37.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/shivammathur/setup-php/security/advisories/GHSA-pqwm-q9pv-ph8r"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/shivammathur/setup-php/commit/eeef37e059fb5368a5bc8ed8ce45ff54bd39b80b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/shivammathur/setup-php"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-78" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-20T15:31:52Z",
    "nvd_published_at" : null
  }
}