CVE-2021-23639 is a critical-severity (CVSS 9.8) remote code execution vulnerability in md-to-pdf. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for md-to-pdf — see the affected versions and patch details below.
Code Injection in md-to-pdf.
EPSS Exploitation Probability
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
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.
md-to-pdfnpmDescription
The package md-to-pdf before 5.0.0 are vulnerable to Remote Code Execution (RCE) due to utilizing the library gray-matter to parse front matter content, without disabling the JS engine.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | md-to-pdf | all versions | 5.0.0npm install md-to-pdf@5.0.0 |
Affected Products
markdown to pdfmarkdown_to_pdf_projectResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for md-to-pdf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update md-to-pdf to 5.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23639 is resolved across your whole dependency graph.
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
Is CVE-2021-23639 in your dependencies?
Find it across npm, including transitive dependencies.