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HIGH severity

CVE-2021-42836 — gjson

HIGHFix: tidwall/gjson@590010f

CVE-2021-42836 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in github.com/tidwall/gjson. 2 public exploit references exist, so weaponization risk is real. A fix is available for github.com/tidwall/gjson — see the affected versions and patch details below.

Duplicate Advisory: ReDoS via crafted JSON input in GJSON

Also known asCVE-2021-42248GHSA-c9gm-7rfj-8w5hGHSA-ppj4-34rq-v8j9GO-2021-0265
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
2 known
Exploitation data as of Oct 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
2.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs84th percentile — riskier than 84% of all scored CVEsHighest risk
0.00%1.03%2.06%3.09%0.2%2.4%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-42836 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
🐹github.com/tidwall/gjson

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

Description

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-ppj4-34rq-v8j9. This link is maintained to preserve external references.

Original Description

GJSON <= 1.9.2 allows attackers to cause a redos via crafted JSON input.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/tidwall/gjsonall versions1.9.3go get github.com/tidwall/gjson@v1.9.3

Affected Products

1 product · 1 configurations
Application
gjsongjson_project
< 1.9.3
range
Exploits & PoCs
2

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

GJSON before 1.9.3 allows a ReDoS (regular expression denial of service)…

github.comNVDOct 2021

GJSON before 1.9.3 allows a ReDoS (regular expression denial of service)…

github.comNVDOct 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update github.com/tidwall/gjson to 1.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42836 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

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-ppj4-34rq-v8j9. This link is maintained to preserve external references. ## Original Description GJSON <= 1.9.2 allows attackers to cause a redos via crafted JSON input.
O3 Security · Impact-Aware SCA

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CVE-2021-42836: gjson — Fixed in 1.9.3