CVE-2021-23385: Flask-Security Project Flask-Security

Medium severity, CVSS 6.1. EPSS: 1.2% chance of exploitation in the next 30 days.

This affects all versions of package Flask-Security. When using the get_post_logout_redirect and get_post_login_redirect functions, it is possible to bypass URL validation and redirect a user to an arbitrary URL by providing multiple back slashes such as \\\evil.com/path. This vulnerability is only exploitable if an alternative WSGI server other than Werkzeug is used, or the default behaviour of Werkzeug is modified using 'autocorrect_location_header=False. **Note:** Flask-Security is not maintained anymore.

Affected products

• Flask-Security Project Flask-Security: any version

Published 2022-08-02. Last modified 2026-06-17.