Redaxo has Path Traversal in Backup Addon Leading to Arbitrary File Read

Summary

Authenticated users with backup permissions can read arbitrary files within the webroot via path traversal in the Backup addon's file export functionality. <img width="664" height="899" alt="image" src="https://github.com/user-attachments/assets/fd1ca69e-b275-4daf-9a62-621cde6525f5" /> <img width="2358" height="445" alt="image" src="https://github.com/user-attachments/assets/fad81152-9e1b-413e-9823-09540a23e2fb" />

Details

The Backup addon does not validate the EXPDIR POST parameter against the UI-generated allowlist of permitted directories.
An attacker can supply relative paths containing ../ sequences (or even absolute paths inside the document root) to include any readable file in the generated .tar.gz archive.

Vulnerable code:

• redaxo/src/addons/backup/pages/export.php (lines 72-76) – directly uses $_POST['EXPDIR']
• redaxo/src/addons/backup/lib/backup.php (lines ~413 & ~427) – concatenates unsanitized user input with base path

This allows disclosure of sensitive files such as:

• redaxo/data/core/config.yml → database credentials + password hashes of all backend users
• .env, custom configuration files, logs, uploaded malicious files, etc.

Affected versions

≤ 5.20.1 (confirmed working)

Patched versions

None (as of 2025-12-09)

PoC – Extracting database credentials and password hashes

1. Log in as any user with Backup permission
2. Go to Backup → Export → Files

<img width="1240" height="960" alt="image" src="https://github.com/user-attachments/assets/bc05ba18-9664-4be2-b637-4fec3a0f409a" />

3. Intercept the request with Burp Suite

<img width="2184" height="478" alt="image" src="https://github.com/user-attachments/assets/9fa754a1-2cd0-4d3d-a5cc-cfa34c8a1718" />

4. Change one EXPDIR[] value to ../../../../var/www/html/redaxo/data/core

<img width="978" height="591" alt="image" src="https://github.com/user-attachments/assets/d15f5c7f-b72c-44cc-9be2-da8d3f26f124" />

5. Send request → download archive <img width="423" height="131" alt="image" src="https://github.com/user-attachments/assets/db8a8bda-cdaf-4dea-812f-1e312da908e2" />

6. Extract and open data/core/config.yml <img width="859" height="281" alt="image" src="https://github.com/user-attachments/assets/c8112ce1-5a1d-435f-953b-7eb4e711e042" />

Result: plaintext database password <img width="2534" height="1198" alt="image" src="https://github.com/user-attachments/assets/218ae917-868a-437e-98b0-6471b82c0b10" />

Impact

Full compromise of the REDAXO installation:

• Database takeover
• Password hash extraction → offline cracking → admin access
• When combined with other vulnerabilities → RCE

CVSS 4.0 vector & score below.

Credits

Discovered by: Łukasz Rybak