Executive brief
FlaskBB is an open-source forum software. A security flaw allows logged-in users to force the forum's server to make unauthorized requests to internal network locations. This could allow an attacker to scan private internal networks, access sensitive cloud metadata (potentially leaking security credentials), or interact with internal management interfaces that are not intended to be public.
Technical details
A Server-Side Request Forgery (SSRF) vulnerability exists in the `get_image_info()` function within `flaskbb/utils/helpers.py`. The application fails to validate the scheme, host, or IP address of URLs provided for user avatars before passing them to the `requests.get()` method. An authenticated attacker can exploit this by submitting a malicious URL (e.g., pointing to 127.0.0.1 or cloud metadata services like 169.254.169.254) via the user settings or admin user-edit pages. This is a blind SSRF that enables internal port scanning through differential error responses and the ability to trigger GET-based internal APIs. The issue is addressed in version 2.2.1 by disabling redirects in the request.
Affected products
- FlaskBB FlaskBB < 2.2.1
Timeline
- 2026-05-19: advisory: GitHub Security Advisory published
- 2026-07-21: disclosed: CVE published to NVD
- 2026-07-21: patched: Version 2.2.1 released