CRITICAL CVSS 9.8
Published: 2021-01-06

CVE-2020-36178

tp-link tl-wr840n_firmware Security Advisory (CVE-2020-36178)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2020-36178 impacting tp-link tl-wr840n_firmware. Evaluated with CVSS Base Score of 9.8 (CRITICAL).

Original NVD Description

Source: NIST NVD
oal_ipt_addBridgeIsolationRules on TP-Link TL-WR840N 6_EU_0.9.1_4.16 devices allows OS command injection because a raw string entered from the web interface (an IP address field) is used directly for a call to the system library function (for iptables). NOTE: oal_ipt_addBridgeIsolationRules is not the only function that calls util_execSystem.

📊 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
High (C:H)
Total information disclosure
Integrity
High (I:H)
Total modification of target system
Availability
High (A:H)
Total denial of service or shutdown

🎯 Affected Versions Matrix

Affected Product tp-link / tl-wr840n_firmware
Affected Versions 6_eu_0.9.1_4.16
Weakness Enumeration CWE-78

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-2020-36178 impacting tp-link tl-wr840n_firmware.

⚡ Nuclei Detection Template (YAML) cve-2020-36178.yaml
id: cve-2020-36178

info:
  name: tp-link tl-wr840n_firmware - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: critical
  description: |
    Automated signature & scanner for CVE-2020-36178 affecting tp-link tl-wr840n_firmware.
    Evaluation: oal_ipt_addBridgeIsolationRules on TP-Link TL-WR840N 6_EU_0.9.1_4.16 devices allows OS command injection because a raw string entered from the web int...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2020-36178
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2020-36178
    cwe-id: CWE-78
  tags: cve,cve-2020-36178,tp-link,tl-wr840n_firmware,critical

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "tl-wr840n_firmware"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2020-36178.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2020-36178
# Target: tp-link tl-wr840n_firmware | CVSS: 9.8 (CRITICAL)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2020-36178 (tp-link tl-wr840n_firmware)...")
    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 tp-link tl-wr840n_firmware scope (6_eu_0.9.1_4.16).")
        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-2020-36178.sh
# Recommended Remediation & Patching Commands for CVE-2020-36178
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install tl-wr840n_firmware 2>/dev/null || \
sudo dnf upgrade tl-wr840n_firmware 2>/dev/null || \
sudo yum update tl-wr840n_firmware

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i tl-wr840n_firmware 2>/dev/null || rpm -qa | grep -i tl-wr840n_firmware

# 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-2020-36178 in tp-link tl-wr840n_firmware?

Review vendor-specific security notices and update tp-link tl-wr840n_firmware 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-2020-36178?

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-2020-36178?

CVE-2020-36178 is classified with a CVSS 3.1 Base Score of 9.8 (CRITICAL). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
9.8
CRITICAL SEVERITY
CVE ID CVE-2020-36178
Weakness CWE-78
Vendor tp-link
Product tl-wr840n_firmware
Published 2021-01-06
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H