{"id":"CVE-2025-66305","aliases":["GHSA-m8vh-v6r6-w7p6"],"url":"https://o3.security/vulnerability/CVE-2025-66305","summary":"Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter","details":"**Endpoint**: `admin/config/system`  \n**Submenu**: `Languages`  \n**Parameter**: `Supported`  \n**Application**: Grav v 1.7.48\n\n---\n\n## Summary\n\nA Denial of Service (DoS) vulnerability was identified in the **\"Languages\"** submenu of the Grav **admin configuration panel** (`/admin/config/system`). Specifically, the `Supported` parameter fails to properly validate user input. If a malformed value is inserted—such as a single forward slash (`/`) or an XSS test string—it causes a fatal regular expression parsing error on the server.\n\nThis leads to application-wide failure due to the use of the `preg_match()` function with an **improperly constructed regular expression**, resulting in the following error:\n\n`preg_match(): Unknown modifier 'o' File: /system/src/Grav/Common/Language/Language.php line 244`\n\nOnce triggered, the site becomes completely unavailable to all users.\n\n---\n\n## Details\n\n- **Vulnerable Endpoint**: `POST /admin/config/system`\n    \n- **Submenu**: `Languages`\n    \n- **Parameter**: `Supported`  \n    \n\nThe application dynamically constructs a regular expression using the contents of the `Supported` field without escaping the input using `preg_quote()` or proper validation. This allows attackers to inject invalid syntax into the regex engine, crashing the application during language resolution.\n\n**Stack trace excerpt**:\n\n`Whoops \\ Exception \\ ErrorException (E_WARNING) preg_match(): Unknown modifier 'o' /system/src/Grav/Common/Language/Language.php244`\n\n---\n\n## Proof of Concept (PoC)\n\n### Payloads:\n\n`/ `\n\n### Steps to Reproduce:\n\n1. Log into the Grav Admin Panel.\n    \n2. Navigate to: **Configuration** → **System** → **Languages**.\n    \n3. Locate the `Supported` field.\n    \n4. Insert one of the payloads above (e.g., a single slash `/`).\n    \n5. Click **Save**.\n\n<img width=\"1897\" height=\"639\" alt=\"Pasted image 20250719183223\" src=\"https://github.com/user-attachments/assets/d3a54a20-d30d-46c6-9015-722f80701cfb\" />\n\n1. Observe: All pages in the application begin throwing a fatal error and become inaccessible.\n\n<img width=\"1802\" height=\"998\" alt=\"Pasted image 20250719175229\" src=\"https://github.com/user-attachments/assets/b16750c2-507f-4c30-a9bb-d07fa92bb777\" />\n\n---\n\n## Impact\n\n- Application-wide Denial of Service (DoS)\n    \n- All login and admin views crash with the same error\n    \n- Potentially exploitable by:\n    \n    - Admin panel users\n        \n    - CSRF if misconfigured        \n    \n\n---\n\n## References\n\n- **CWE-1333**: Improper Regular Expression\n    \n- **CWE-20**: Improper Input Validation\n\n\n## Discoverer\n\n[Marcelo Queiroz](www.linkedin.com/in/marceloqueirozjr) \n\nby [CVE-Hunters](https://github.com/Sec-Dojo-Cyber-House/cve-hunters)","published":"2025-12-01T21:43:29.725Z","modified":"2026-08-12T03:51:22.483120215Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"getgrav/grav","fixedVersion":"1.8.0-beta.27"}],"fix":{"url":"https://github.com/getgrav/grav/commit/ed640a13143c4177af013cf001969ed2c5e197ee","label":"getgrav/grav@ed640a1"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/66xxx/CVE-2025-66305.json"},{"type":"ADVISORY","url":"https://github.com/getgrav/grav/security/advisories/GHSA-m8vh-v6r6-w7p6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-66305"},{"type":"FIX","url":"https://github.com/getgrav/grav/commit/ed640a13143c4177af013cf001969ed2c5e197ee"},{"type":"PACKAGE","url":"https://github.com/getgrav/grav"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:22.483120215Z"}}