Open redirect in Flask-User
Priority LOW 29CWE-601Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- Spoofing
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-601.
Summary
This affects all versions of package Flask-User. When using the make_safe_url function, 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 or \\\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.
Why it matters now
EPSS 0.01113 66th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix No fix listed No fixed version in the sources yet
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | Flask-User | all versions | — | No fix listed | CNA |
| — | Flask-User (PyPI) | up to 1.0.2.2 | — | No fix listed | GHSA-4298-89hc-6rfv |
- Flask-User Vendor— Affected all versions Fixed in — No fix listed CNA
- Flask-User (PyPI) Vendor— Affected up to 1.0.2.2 Fixed in — No fix listed GHSA-4298-89hc-6rfv
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:flask-user_project:flask-user:*:*:*:*:*:*:*:* | all versions | Vulnerable | Flask-user Project |
- cpe:2.3:a:flask-user_project:flask-user:*:*:*:*:*:*:*:* Versions all versions Vulnerable ·Flask-user Project
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2021-23401
- 2026-10-03 Alias added: GHSA-4298-89hc-6rfv
References
Advisory 3
Sources
- CVE-2021-23401 · CVE Program
- CVE-2021-23401 · NVD
- FIRST EPSS
- GHSA-4298-89hc-6rfv · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences