MEDIUM CVSS 4.1
Published: 2026-03-19

CVE-2026-27166

discourse discourse Security Advisory (CVE-2026-27166)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-27166 impacting discourse discourse. Evaluated with CVSS Base Score of 4.1 (MEDIUM).

Original NVD Description

Source: NIST NVD
Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes.

📊 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
Low (PR:L)
Standard user access required
User Interaction
Required (UI:R)
User must click or open resource
Scope
Changed (S:C)
Impacts components beyond caller authority
Confidentiality
None (C:N)
No data confidentiality impact
Integrity
Low (I:L)
Partial data modification possible
Availability
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product discourse / discourse
Affected Versions *
Weakness Enumeration CWE-80

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-2026-27166 impacting discourse discourse.

⚡ Nuclei Detection Template (YAML) cve-2026-27166.yaml
id: cve-2026-27166

info:
  name: discourse discourse - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-27166 affecting discourse discourse.
    Evaluation: Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and  2026.1.2, insufficient cleanup in the default Code...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-27166
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N
    cvss-score: 4.1
    cve-id: CVE-2026-27166
    cwe-id: CWE-80
  tags: cve,cve-2026-27166,discourse,discourse,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "discourse"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-27166.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-27166
# Target: discourse discourse | CVSS: 4.1 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-27166 (discourse discourse)...")
    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 discourse discourse 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-2026-27166.sh
# Recommended Remediation & Patching Commands for CVE-2026-27166
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install discourse 2>/dev/null || \
sudo dnf upgrade discourse 2>/dev/null || \
sudo yum update discourse

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

# 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.

🔗 Verified Technical References

Authorities
  • No records filed in this category.
Distributions
  • No records filed in this category.

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-27166 in discourse discourse?

Review vendor-specific security notices and update discourse discourse 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-2026-27166?

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-2026-27166?

CVE-2026-27166 is classified with a CVSS 3.1 Base Score of 4.1 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
4.1
MEDIUM SEVERITY
CVE ID CVE-2026-27166
Weakness CWE-80
Vendor discourse
Product discourse
Published 2026-03-19
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N