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HIGH severity

CVE-2020-8268 — json8-merge-patch

HIGHFix: sonnyp/JSON8@2e89026

CVE-2020-8268 is a high-severity (CVSS 7.5) CWE-471 vulnerability in json8-merge-patch. 1 public exploit reference exists, so weaponization risk is real. A fix is available for json8-merge-patch — see the affected versions and patch details below.

Prototype pollution in json8-merge-patch

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs70th percentile — riskier than 70% of all scored CVEsHighest risk
0.00%0.60%1.20%1.79%0.2%1.3%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2020-8268 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 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

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

1other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
json8-merge-patchnpm
1Kdownloads / week

Description

Prototype pollution vulnerability in json8-merge-patch npm package < 1.0.3 may allow attackers to inject or modify methods and properties of the global object constructor.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmjson8-merge-patchall versions1.0.3npm install json8-merge-patch@1.0.3

Affected Products

1 product · 1 configurations
Application
json8-merge-patchjson8-merge-patch_project
< 1.0.3
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.

Prototype pollution vulnerability in json8-merge-patch npm package < 1.0…

hackerone.comNVDNov 2020

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for json8-merge-patch, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update json8-merge-patch to 1.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-8268 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

Prototype pollution vulnerability in json8-merge-patch npm package < 1.0.3 may allow attackers to inject or modify methods and properties of the global object constructor.
O3 Security · Impact-Aware SCA

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CVE-2020-8268: json8-merge-patch — Fixed in 1.0.3