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Not in CISA KEV
HIGH severity

Webargs mishandles concurrent JSON parsingGHSA-8554-jxcw-454q

HIGHFix: marshmallow-code/webargs#373

GHSA-8554-jxcw-454q is a high-severity (CVSS 8.1) CWE-362 vulnerability in webargs. 1 public exploit reference exists, so weaponization risk is real. A fix is available for webargs — see the affected versions and patch details below.

Also known asCVE-2019-9710PYSEC-2019-139
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.1%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs65th percentile — riskier than 65% of all scored CVEsHighest risk
0.00%0.54%1.09%1.63%0.4%1.1%Apr 26Aug 26Oct 26

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

How urgent is this, really

GHSA-8554-jxcw-454q 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
🐍webargs

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

An issue was discovered in webargs before 5.1.3, as used with marshmallow and other products. JSON parsing uses a short-lived cache to store the parsed JSON body. This cache is not thread-safe, meaning that incorrect JSON payloads could have been parsed for concurrent requests.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIwebargsall versions5.1.3pip install --upgrade 'webargs==5.1.3'

Affected Products

1 product · 1 configurations
Application
webargswebargs_project
< 5.1.3
range
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

An issue was discovered in webargs before 5.1.3, as used with marshmallo…

github.comNVDMar 2019

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update webargs to 5.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-8554-jxcw-454q 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

An issue was discovered in webargs before 5.1.3, as used with marshmallow and other products. JSON parsing uses a short-lived cache to store the parsed JSON body. This cache is not thread-safe, meaning that incorrect JSON payloads could have been parsed for concurrent requests.
O3 Security · Impact-Aware SCA

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Webargs mishandles concurrent JSON parsing (High 8.1)