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Not in CISA KEV
HIGH severity

CVE-2021-32838 — flask-restx

HIGHFix: python-restx/flask-restx@bab31e0

CVE-2021-32838 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in flask-restx. A fix is available for flask-restx — see the affected versions and patch details below.

Regular Expression Denial of Service in flask-restx

Also known asGHSA-3q6g-vf58-7m4gPYSEC-2021-325
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk
0.87%1.37%1.86%2.36%1.4%1.9%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-32838 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 386,684 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-restx

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

Flask-RESTX (pypi package flask-restx) is a community driven fork of Flask-RESTPlus. Flask-RESTX before version 0.5.1 is vulnerable to ReDoS (Regular Expression Denial of Service) in email_regex. This is fixed in version 0.5.1.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIflask-restxall versions0.5.1pip install --upgrade 'flask-restx==0.5.1'

Affected Products

2 products · 3 configurations
OS
fedorafedoraproject
2 versions
3334
Application
flask-restxflask-restx_project
< 0.5.1
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-restx, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update flask-restx to 0.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32838 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

Flask-RESTX (pypi package flask-restx) is a community driven fork of Flask-RESTPlus. Flask-RESTX before version 0.5.1 is vulnerable to ReDoS (Regular Expression Denial of Service) in email_regex. This is fixed in version 0.5.1.
O3 Security · Impact-Aware SCA

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CVE-2021-32838: flask-restx DoS — Fixed in 0.5.1