# CVE-2021-41265: Improper Authentication in Flask-AppBuilder

Source: https://junglewise.ai/threats/cve-2021-41265-improper-authentication-in-flask-appbuilder  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-12-09  
License: CC BY 4.0 with a link back

CVE-2021-41265 · Severity: low · CVSS 3.1 · Published 2021-12-09

Flask-AppBuilder is a development framework built on top of Flask. Verions prior to 3.3.4 contain an improper authentication vulnerability in the REST API. The issue allows for a malicious actor with a carefully crafted request to successfully authenticate and gain access to existing protected REST API endpoints. This only affects non database authentication types and new REST API endpoints. Users should upgrade to Flask-AppBuilder 3.3.4 to receive a patch.

Technologies: [flask-appbuilder (PyPI)](https://junglewise.ai/threats/technologies/flask-appbuilder). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-41265 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-41265 being exploited in the wild.

**How severe is CVE-2021-41265?** Low severity, with a CVSS score of 3.1, published 9 December 2021.

**Which products and versions are affected?** flask-appbuilder (PyPI) ECOSYSTEM:introduced=0,fixed=3.3.4, GIT:introduced=0,fixed=eba517aab121afa3f3f2edb011ec6bc4efd61fbc|ECOSYSTEM:introduced=0,fixed=3.3.4.

**Is there a fix for CVE-2021-41265?** Yes. flask-appbuilder (PyPI): upgrade to 3.3.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-41265?** Check whether you run flask-appbuilder (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- flask-appbuilder (PyPI): upgrade to 3.3.4 or later

  ```sh
  pip install "flask-appbuilder>=3.3.4"
  ```


## Affected products

- flask-appbuilder (PyPI) ECOSYSTEM:introduced=0,fixed=3.3.4, GIT:introduced=0,fixed=eba517aab121afa3f3f2edb011ec6bc4efd61fbc|ECOSYSTEM:introduced=0,fixed=3.3.4

## Identifiers

- CVE-2021-41265
- GHSA-m3rf-7m4w-r66q
- PYSEC-2021-851

## Related threats

- [PYSEC-2026-1378 - Flask App Builder has an Authentication Bypass vulnerability when using non AUTH_DB methods](https://junglewise.ai/threats/cve-2025-58065-flask-app-builder-has-an-authentication-bypass-vulnerability-when)
- [PYSEC-2026-1379 - Flask-AppBuilder open redirect vulnerability using HTTP host injection](https://junglewise.ai/threats/cve-2025-32962-flask-appbuilder-open-redirect-vulnerability-using-http-host)
- [PYSEC-2026-1382 - Flask-AppBuilder's login form allows browser to cache sensitive fields](https://junglewise.ai/threats/cve-2024-45314-flask-appbuilder-s-login-form-allows-browser-to-cache-sensitive)
- [PYSEC-2026-1381 - Flask-AppBuilder's OAuth login page subject to Cross Site Scripting (XSS)](https://junglewise.ai/threats/cve-2024-27083-flask-appbuilder-s-oauth-login-page-subject-to-cross-site)
- [PYSEC-2026-1380 - Flask-AppBuilder Has No Rate Limiting on Login AUTH DB](https://junglewise.ai/threats/cve-2023-29005-flask-appbuilder-has-no-rate-limiting-on-login-auth-db)