---
id: CVE-2021-29621
aliases:
  - GHSA-434h-p4gx-jm89
  - BIT-airflow-2021-29621
  - PYSEC-2021-90
title: Observable Response Discrepancy in Flask-AppBuilder
summary: Observable Response Discrepancy in Flask-AppBuilder
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
vendor: flask-appbuilder
product: flask-appbuilder
ecosystem: pip
affected:
  - flask-appbuilder < 3.3.0
patched:
  - flask-appbuilder 3.3.0
published: '2021-05-27'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-434h-p4gx-jm89'
references:
  - url: >-
      https://github.com/dpgaspar/Flask-AppBuilder/security/advisories/GHSA-434h-p4gx-jm89
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-29621'
  - url: >-
      https://github.com/dpgaspar/Flask-AppBuilder/commit/780bd0e8fbf2d36ada52edb769477e0a4edae580
  - url: 'https://github.com/dpgaspar/Flask-AppBuilder'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/flask-appbuilder/PYSEC-2021-90.yaml
  - url: >-
      https://lists.apache.org/thread.html/r466759f377651f0a690475d5a52564d0e786e82c08d5a5730a4f8352%40%3Cannounce.apache.org%3E
  - url: >-
      https://lists.apache.org/thread.html/r466759f377651f0a690475d5a52564d0e786e82c08d5a5730a4f8352@%3Cannounce.apache.org%3E
  - url: >-
      https://lists.apache.org/thread.html/r5b754118ba4e996adf03863705d34168bffec202da5c6bdc9bf3add5%40%3Cannounce.apache.org%3E
  - url: >-
      https://lists.apache.org/thread.html/r5b754118ba4e996adf03863705d34168bffec202da5c6bdc9bf3add5@%3Cannounce.apache.org%3E
  - url: >-
      https://lists.apache.org/thread.html/r91067f953906d93aaa1c69fe2b5472754019cc6bd4f1ba81349d62a0%40%3Ccommits.airflow.apache.org%3E
  - url: >-
      https://lists.apache.org/thread.html/r91067f953906d93aaa1c69fe2b5472754019cc6bd4f1ba81349d62a0@%3Ccommits.airflow.apache.org%3E
  - url: 'https://pypi.org/project/Flask-AppBuilder'
tags:
  - osv
  - pip
epss: 0.03404
epssPercentile: 0.88423
ingestedAt: '2026-07-08T18:25:45.230Z'
---

## Overview

### Impact
User enumeration in database authentication in Flask-AppBuilder <= 3.2.3. Allows for a non authenticated user to enumerate existing accounts by timing the response time from the server when you are logging in.

### Patches
Upgrade to 3.3.0

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [Flask-AppBuilder](https://github.com/dpgaspar/Flask-AppBuilder)

## Affected packages

- `flask-appbuilder < 3.3.0`

## Remediation

Upgrade to a patched release:

- `flask-appbuilder 3.3.0`