GHSA-3446-6mgw-f79p

Dear Grav Security Team, A security vulnerability was discovered in Grav CMS that allows authenticated attackers to read arbitrary files from the server through XML External Entity (XXE) injection. Vulnerability Summary | Field | Details | |-------|---------| | Vulnerability Type | XML External Entity (XXE) Injection | | Severity | High (CVSS 7.5) | | Affected Versions | Grav CMS <= 1.7.x | | Affected Component | SVG file upload/processing | | CWE | CWE-611: Improper Restriction of XML External Entity Reference | | Authentication Required | Yes (Admin panel access) | Technical Details Root Cause The application uses `simplexml_load_string()` to process uploaded SVG files without disabling external entity loading. This allows attackers to inject XXE payloads that are processed by the XML parser. Vulnerable Code Pattern ```php // Current (Vulnerable): $svg = simplexml_load_string($content); // No LIBXML_NOENT flag or entity loader protection ``` Attack Vector 1. Attacker authenticates to Grav admin panel 2. Uploads malicious SVG file via Pages → Media or File Manager plugin 3. Server parses SVG and processes XXE entities 4. Arbitrary file contents are exfiltrated Impact An authenticated attacker can: 1. Read sensitive files: - `/etc/passwd` - System user information - `user/accounts/*.yaml` - Admin credentials and 2FA secrets - `user/config/system.yaml` - System configuration - `.env` files - Environment secrets and API keys 2. Perform SSRF - Access internal services via external entity URLs 3. Potential DoS - Billion laughs attack via recursive entity expansion Proof of Concept Malicious SVG Payload ```xml <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE svg [ <!ENTITY xxe SYSTEM "file:///etc/passwd"> ]> <svg xmlns="http://www.w3.org/2000/svg" width="100" height="100"> <text x="10" y="50">&xxe;</text> </svg> ``` Steps to Reproduce 1. Login to Grav CMS admin panel 2. Navigate to Pages → select any page → Media tab 3. Upload the m