PYSEC-2026-341

### Impact A critical path traversal and extension bypass vulnerability in Flask-Reuploaded allows remote attackers to achieve arbitrary file write and remote code execution through Server-Side Template Injection (SSTI).

### Patches Flask-Reuploaded has been patched in version 1.5.0

### Workarounds

1. **Do not pass user input to the `name` parameter** 2. Use auto-generated filenames only 3. Implement strict input validation if `name` must be used

```python from werkzeug.utils import secure_filename import os

# Sanitize user input before passing to save() safe_name = secure_filename(request.form.get('custom_name')) # Remove path separators safe_name = os.path.basename(safe_name) # Validate extension matches policy if not photos.extension_allowed(photos.get_extension(safe_name)): abort(400) filename = photos.save(file, name=safe_name) ```

### Resources The fix is documented in the pull request, see https://github.com/jugmac00/flask-reuploaded/pull/180. A proper write-up was created by the reporter of the vulnerability, Jaron Cabral (https://www.linkedin.com/in/jaron-cabral-751994357/), but is not yet available as of time of this publication.