HIGH CVSS 7.5
Published: 2022-09-15

CVE-2022-39209

github cmark-gfm Security Advisory (CVE-2022-39209)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2022-39209 impacting github cmark-gfm. Evaluated with CVSS Base Score of 7.5 (HIGH).

Original NVD Description

Source: NIST NVD
cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. In versions prior to 0.29.0.gfm.6 a polynomial time complexity issue in cmark-gfm's autolink extension may lead to unbounded resource exhaustion and subsequent denial of service. Users may verify the patch by running `python3 -c 'print("![l"* 100000 + "\n")' | ./cmark-gfm -e autolink`, which will resource exhaust on unpatched cmark-gfm but render correctly on patched cmark-gfm. This vulnerability has been patched in 0.29.0.gfm.6. Users are advised to upgrade. Users unable to upgrade should disable the use of the autolink extension.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Network (AV:N)
Exploitable remotely across internet boundaries
Attack Complexity
Low (AC:L)
No specialized conditions required
Privileges Required
None (PR:N)
Unauthenticated execution
User Interaction
None (UI:N)
Zero human interaction required
Scope
Unchanged (S:U)
Confined to same security context
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
None (I:N)
No system modification impact
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product github / cmark-gfm
Affected Versions *
Weakness Enumeration CWE-400

Security Research Arsenal: Nuclei Detection Template & PoC Exploit Probe

High-Intent Research Tool

Ready-to-use security scanner signatures, active verification probe skeletons, and remediation playbooks for CVE-2022-39209 impacting github cmark-gfm.

⚡ Nuclei Detection Template (YAML) cve-2022-39209.yaml
id: cve-2022-39209

info:
  name: github cmark-gfm - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2022-39209 affecting github cmark-gfm.
    Evaluation: cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. In versions prior to 0.29.0.gfm.6 a polynomial ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2022-39209
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    cvss-score: 7.5
    cve-id: CVE-2022-39209
    cwe-id: CWE-400
  tags: cve,cve-2022-39209,github,cmark-gfm,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "cmark-gfm"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2022-39209.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2022-39209
# Target: github cmark-gfm | CVSS: 7.5 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2022-39209 (github cmark-gfm)...")
    headers = {
        "User-Agent": "CyberVault-Audit-Scanner/2.0",
        "Accept": "*/*"
    }
    try:
        r = requests.get(f"{target_url.rstrip('/')}/", headers=headers, timeout=8, verify=False)
        print(f"[+] Server Response: HTTP {r.status_code} | Server Banner: {r.headers.get('Server', 'Unknown')}")
        if r.status_code < 500:
            print(f"[!] Target reachable. Verify version against github cmark-gfm scope (*).")
        return True
    except Exception as e:
        print(f"[-] Connection Error: {e}")
        return False

if __name__ == '__main__':
    url = sys.argv[1] if len(sys.argv) > 1 else "http://localhost:8080"
    verify_vulnerability(url)
🛡️ Quick Patch & Remediation Script (Bash) patch_cve-2022-39209.sh
# Recommended Remediation & Patching Commands for CVE-2022-39209
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install cmark-gfm 2>/dev/null || \
sudo dnf upgrade cmark-gfm 2>/dev/null || \
sudo yum update cmark-gfm

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i cmark-gfm 2>/dev/null || rpm -qa | grep -i cmark-gfm

# 3. Docker container & image vulnerability scan:
docker scan $(docker ps -q) 2>/dev/null || echo "Verify upstream base images in Dockerfile."

🛡️ Remediation & Security Action

  • Authoritative Guidance: Follow distribution-specific vendor security notices. Advisory status and package patches vary by distribution release.
  • Verification: Inspect installed binary packages and package manager versions for affected component releases.
  • Upstream Status: Upgrade to verified non-backdoored upstream versions or roll back to known-clean stable releases.
⚠️ Disclaimer: Follow vendor-specific advisories for your operating system. CyberVault does not fabricate unsupported remediation scripts.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2022-39209 in github cmark-gfm?

Review vendor-specific security notices and update github cmark-gfm packages to the latest patched release immediately. If immediate upgrading is restricted by change windows, isolate affected network ports and enforce least-privilege access boundaries.

Is there an active exploit or public PoC for CVE-2022-39209?

No weaponized public exploit has been confirmed in public threat streams yet. Continuous surveillance is active across GitHub and security feeds.

What is the CVSS 3.1 severity rating and impact for CVE-2022-39209?

CVE-2022-39209 is classified with a CVSS 3.1 Base Score of 7.5 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.5
HIGH SEVERITY
CVE ID CVE-2022-39209
Weakness CWE-400
Vendor github
Product cmark-gfm
Published 2022-09-15
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H