GHSA-vwg3-w8w3-pc79 Grav: .htaccess file extension rules bypass via case variation on case-insensitive filesystems

• Packagist getgrav/grav: < 2.0.4 → fixed in 2.0.4

Summary The default `.htaccess` shipped with Grav (and the reference `webserver-configs/htaccess.txt`) contains security rules that block direct HTTP access to sensitive file types (`.yaml`, `.yml`, `.php`, `.json`, `.twig`, etc.) under `user/` and `system/vendor/` directories. However, these rules lack the `[NC]` (No Case) flag, making them case-sensitive. On case-insensitive filesystems (Windows/NTFS, macOS/HFS+, or Linux with Docker volumes mounted from Windows/macOS), an attacker can bypass these rules by requesting files with uppercase extensions (e.g., `.YAML`, `.PHP`, `.JSON`). Affected Versions • Grav 2.0.1 (latest stable as of June 2026) — confirmed • Grav 1.7.x — likely affected (same `.htaccess` rules) • All versions shipping the current `webserver-configs/htaccess.txt` Affected Component File: `.htaccess` (root of Grav installation) Reference: `webserver-configs/htaccess.txt` Affected Rules (lines 68, 70, 72) ```apache Line 68 — system/vendor file types RewriteRule ^(system|vendor)/(.*)\.(txt|xml|md|html|htm|shtml|shtm|json|yaml|yml|php|php2|php3|php4|php5|phar|phtml|pl|py|cgi|twig|sh|bat)$ error [F] Line 70 — user file types RewriteRule ^(user)/(.*)\.(txt|md|json|yaml|yml|php|php2|php3|php4|php5|phar|phtml|pl|py|cgi|twig|sh|bat)$ error [F] Line 72 — .md files globally RewriteRule \.md$ error [F] ``` All three rules use `[F]` without `[NC]`, making the extension match case-sensitive. Steps to Reproduce 1. Install Grav on a system with a case-insensitive filesystem: • Windows (native WAMP/XAMPP) • macOS (default HFS+) • Docker on Windows/macOS with volume mounts (e.g., `./data:/var/www/html`) 2. Create or use any plugin that stores sensitive data in its YAML config (e.g., API keys): ``` user/plugins/my-plugin/my-plugin.yaml ``` 3. Request the file with a case-varied extension: ``` GET /user/plugins/my-plugin/my-plugin.YAML HTTP/1.1 ``` 4. Expected: HTTP 403 Forbidden 5. Actual: HTTP 200 OK — full file contents returned, including any API keys or sensitive configuration Impact • Information disclosure: Plugin configuration files (`.yaml`) containing API keys, credentials, or sensitive settings can be read by unauthenticated users • Source code exposure: PHP source files can be downloaded (instead of executed) when requested with `.PHP` extension on some configurations • Configuration exposure: `user/config/system.yaml`, `user/config/site.yaml`, and other system configuration files are accessible Fix Add the `[NC]` flag to the three affected rules: ```apache RewriteRule ^(system|vendor)/(.*)\.(txt|xml|md|html|htm|shtml|shtm|json|yaml|yml|php|php2|php3|php4|php5|phar|phtml|pl|py|cgi|twig|sh|bat)$ error [F,NC] RewriteRule ^(user)/(.*)\.(txt|md|json|yaml|yml|php|php2|php3|php4|php5|phar|phtml|pl|py|cgi|twig|sh|bat)$ error [F,NC] RewriteRule \.md$ error [F,NC] ``` The `[NC]` flag makes the extension matching case-insensitive, covering `.YAML`, `.Yaml`, `.PHP`, `.Json`, etc. Mitigating Factors • On native Linux with ext4 filesystem (case-sensitive), the attack does not work because Apache cannot resolve the uppercase filename to the actual file • Grav 2.0's Twig sandbox blocks access to `plugins` config subtree from page content, preventing SSTI-based config exfiltration • The `user/accounts/`, `user/config/`, and `user/data/` folders have separate rules (line 62, 66) that block ALL file types regardless of extension — these are not affected Environment • Grav: 2.0.1 • PHP: 8.3 • Apache: 2.4 with mod_rewrite • OS: Docker (php:8.3-apache) with volume mounted from Windows 10 (NTFS) • Tested: June 2026 Reporter Sisnetic