HIGH CVSS 7.3
Published: 2023-08-09

CVE-2023-36673

avira phantom_vpn Security Advisory (CVE-2023-36673)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2023-36673 impacting avira phantom_vpn. Evaluated with CVSS Base Score of 7.3 (HIGH).

Original NVD Description

Source: NIST NVD
An issue was discovered in Avira Phantom VPN through 2.23.1 for macOS. The VPN client insecurely configures the operating system such that all IP traffic to the VPN server's IP address is sent in plaintext outside the VPN tunnel, even if this traffic is not generated by the VPN client, while simultaneously using plaintext DNS to look up the VPN server's IP address. This allows an adversary to trick the victim into sending traffic to arbitrary IP addresses in plaintext outside the VPN tunnel. NOTE: the tunnelcrack.mathyvanhoef.com website uses this CVE ID to refer more generally to "ServerIP attack, combined with DNS spoofing, that can leak traffic to an arbitrary IP address" rather than to only Avira Phantom VPN.

📊 CVSS v3.1 Metric Breakdown

Attack Vector
Adjacent (AV:A)
Requires shared subnet / local network access
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
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
None (A:N)
No system availability impact

🎯 Affected Versions Matrix

Affected Product avira / phantom_vpn
Affected Versions *
Weakness Enumeration CWE-319

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-2023-36673 impacting avira phantom_vpn.

⚡ Nuclei Detection Template (YAML) cve-2023-36673.yaml
id: cve-2023-36673

info:
  name: avira phantom_vpn - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2023-36673 affecting avira phantom_vpn.
    Evaluation: An issue was discovered in Avira Phantom VPN through 2.23.1 for macOS. The VPN client insecurely configures the operating system such that all IP traf...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2023-36673
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
    cvss-score: 7.3
    cve-id: CVE-2023-36673
    cwe-id: CWE-319
  tags: cve,cve-2023-36673,avira,phantom_vpn,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "phantom_vpn"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2023-36673.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2023-36673
# Target: avira phantom_vpn | CVSS: 7.3 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2023-36673 (avira phantom_vpn)...")
    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 avira phantom_vpn 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-2023-36673.sh
# Recommended Remediation & Patching Commands for CVE-2023-36673
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install phantom_vpn 2>/dev/null || \
sudo dnf upgrade phantom_vpn 2>/dev/null || \
sudo yum update phantom_vpn

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

# 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-2023-36673 in avira phantom_vpn?

Review vendor-specific security notices and update avira phantom_vpn 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-2023-36673?

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-2023-36673?

CVE-2023-36673 is classified with a CVSS 3.1 Base Score of 7.3 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
7.3
HIGH SEVERITY
CVE ID CVE-2023-36673
Weakness CWE-319
Vendor avira
Product phantom_vpn
Published 2023-08-09
Vector CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N