MEDIUM CVSS 6.1
Published: 2026-04-01

CVE-2026-35055

xenforo xenforo Security Advisory (CVE-2026-35055)
↗ Official NIST NVD Record
Seeking technical exploit breakdowns or verified PoC code for CVE-2026-35055?
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-35055 impacting xenforo xenforo. Evaluated with CVSS Base Score of 6.1 (MEDIUM).

Original NVD Description

Source: NIST NVD
XenForo before 2.3.9 and before 2.2.18 is vulnerable to cross-site scripting (XSS) related to lightbox usage in posts. An attacker can inject malicious scripts that execute when users interact with post content displayed in the lightbox.

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

🎯 Affected Versions Matrix

Affected Product xenforo / xenforo
Affected Versions *
Weakness Enumeration CWE-79

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-2026-35055 impacting xenforo xenforo.

⚡ Nuclei Detection Template (YAML) cve-2026-35055.yaml
id: cve-2026-35055

info:
  name: xenforo xenforo - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-35055 affecting xenforo xenforo.
    Evaluation: XenForo before 2.3.9 and before 2.2.18 is vulnerable to cross-site scripting (XSS) related to lightbox usage in posts. An attacker can inject maliciou...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-35055
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2026-35055
    cwe-id: CWE-79
  tags: cve,cve-2026-35055,xenforo,xenforo,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "xenforo"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-35055.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-35055
# Target: xenforo xenforo | CVSS: 6.1 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-35055 (xenforo xenforo)...")
    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 xenforo xenforo 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-2026-35055.sh
# Recommended Remediation & Patching Commands for CVE-2026-35055
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install xenforo 2>/dev/null || \
sudo dnf upgrade xenforo 2>/dev/null || \
sudo yum update xenforo

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

# 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

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-35055 in xenforo xenforo?

Review vendor-specific security notices and update xenforo xenforo 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-2026-35055?

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-2026-35055?

CVE-2026-35055 is classified with a CVSS 3.1 Base Score of 6.1 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
6.1
MEDIUM SEVERITY
CVE ID CVE-2026-35055
Weakness CWE-79
Vendor xenforo
Product xenforo
Published 2026-04-01
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N