Improper Authentication in Flask-AppBuilder

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.6 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2021-41265: 1.32% estimated exploitation activity in the next 30 days; percentile 70.82 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Improper authentication on the REST API. Allows for a malicious actor with a carefully crafted request to successfully authenticate and gain access to existing protected REST API endpoints. Only affects non database authentication types, and new REST API endpoints. Patches Upgrade to Flask-AppBuilder 3.3.4 For more information If you have any questions or comments about this advisory: Open an issue in https://github.com/dpgaspar/Flask-AppBuilder

Published by the source

9 Dec 2021, 19:09 UTC

Last modified by the source

8 Jul 2026, 06:29 UTC

Source last checked

26 Oct 2026, 13:31 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m3rf-7m4w-r66q

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m3rf-7m4w-r66q

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# Patch Next advisory brief: CVE-2021-41265

Advisory: Improper Authentication in Flask-AppBuilder
IDs: CVE-2021-41265, GHSA-m3rf-7m4w-r66q
Record: https://patchnext.com/advisories/cve-2021-41265 (revision 3, source checked 26 Oct 2026, 13:31 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flask-appbuilder 3.3.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flask-appbuilder: affected < 3.3.4; fixed in 3.3.4

## Suggested inspection (read-only)
- `python -m pip show flask-appbuilder`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flask-appbuilder.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-m3rf-7m4w-r66q (OSV record GHSA-m3rf-7m4w-r66q lists affected ranges: PyPI flask-appbuilder >=0 <3.3.4 (fixed))
- Verified: https://github.com/advisories/GHSA-m3rf-7m4w-r66q (GitHub-reviewed advisory GHSA-m3rf-7m4w-r66q lists affected ranges: PyPI flask-appbuilder >=0 <3.3.4)

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