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MEDIUM severity

Observable Response Discrepancy in Flask-AppBuilderGHSA-434h-p4gx-jm89

MEDIUMFix: dpgaspar/Flask-AppBuilder@780bd0e

GHSA-434h-p4gx-jm89 is a medium-severity (CVSS 5.3) CWE-203 vulnerability in flask-appbuilder. A fix is available for flask-appbuilder — see the affected versions and patch details below.

Also known asBIT-airflow-2021-29621CVE-2021-29621PYSEC-2021-90
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
3.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs89th percentile — riskier than 89% of all scored CVEsHighest risk
0.00%1.43%2.86%4.30%0.4%3.4%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-434h-p4gx-jm89 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐍flask-appbuilder

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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:

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIflask-appbuilderall versions3.3.0pip install --upgrade 'flask-appbuilder==3.3.0'

Affected Products

2 products · 2 configurations
Application
airflowapache
1 version
1.10.0
Application
flask-appbuilderdpgaspar
≤ 3.2.3
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flask-appbuilder, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update flask-appbuilder to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-434h-p4gx-jm89 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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)
O3 Security · Impact-Aware SCA

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Observable Response Discrepancy in Flask-AppBuilder