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Not in CISA KEV
HIGH severity

CVE-2021-43308 — markdown-link-extractor

HIGH

CVE-2021-43308 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in markdown-link-extractor. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for markdown-link-extractor — see the affected versions and patch details below.

Regular expression denial of service in markdown-link-extractor

Also known asGHSA-mmh6-m7v9-5956
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
1 known
Exploitation data as of Nov 6, 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 CVEs66th percentile — riskier than 66% of all scored CVEsHighest risk
0.00%0.53%1.06%1.60%0.4%1.1%May 26Sep 26Nov 26

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs 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.

98other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
markdown-link-extractornpm
280Kdownloads / week

Description

An exponential ReDoS (Regular Expression Denial of Service) can be triggered in the markdown-link-extractor npm package, when an attacker is able to supply arbitrary input to the module's exported function

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
📦npmmarkdown-link-extractorall versions3.0.2npm install markdown-link-extractor@3.0.2
📦npmmarkdown-link-extractor≥ 4.0.0&&< 4.0.14.0.1npm install markdown-link-extractor@4.0.1

Affected Products

1 product · 2 configurations
Application
markdown-link-extractormarkdown-link-extractor_project
< 3.0.2
1 version
4.0.0
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 exponential ReDoS (Regular Expression Denial of Service) can be trigg…

research.jfrog.comNVDJun 2022

Detection & mitigation playbook

Open-source dependency

  1. Detect

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

  2. Fix

    Update markdown-link-extractor to 3.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43308 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

An exponential ReDoS (Regular Expression Denial of Service) can be triggered in the markdown-link-extractor npm package, when an attacker is able to supply arbitrary input to the module's exported function
O3 Security · Impact-Aware SCA

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CVE-2021-43308: markdown-link DoS — Fixed in 3.0.2