MEDIUM CVSS 5.7
Published: 2026-04-02

CVE-2026-30867

emqx cocoamqtt Security Advisory (CVE-2026-30867)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-30867 impacting emqx cocoamqtt. Evaluated with CVSS Base Score of 5.7 (MEDIUM).

Original NVD Description

Source: NIST NVD
CocoaMQTT is a MQTT 5.0 client library for iOS and macOS written in Swift. Prior to version 2.2.2, a vulnerability exists in the packet parsing logic of CocoaMQTT that allows an attacker (or a compromised/malicious MQTT broker) to remotely crash the host iOS/macOS/tvOS application. If an attacker publishes the 4-byte malformed payload to a shared topic with the RETAIN flag set to true, the MQTT broker will persist the payload. Any time a vulnerable client connects and subscribes to that topic, the broker will automatically push the malformed packet. The app will instantly crash in the background before the user can even interact with it. This effectively "bricks" the mobile application (a persistent DoS) until the retained message is manually wiped from the broker database. This issue has been patched in version 2.2.2.

📊 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
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 emqx / cocoamqtt
Affected Versions *
Weakness Enumeration CWE-617

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-2026-30867 impacting emqx cocoamqtt.

⚡ Nuclei Detection Template (YAML) cve-2026-30867.yaml
id: cve-2026-30867

info:
  name: emqx cocoamqtt - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: medium
  description: |
    Automated signature & scanner for CVE-2026-30867 affecting emqx cocoamqtt.
    Evaluation: CocoaMQTT is a MQTT 5.0 client library for iOS and macOS written in Swift. Prior to version 2.2.2, a vulnerability exists in the packet parsing logic ...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-30867
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
    cvss-score: 5.7
    cve-id: CVE-2026-30867
    cwe-id: CWE-617
  tags: cve,cve-2026-30867,emqx,cocoamqtt,medium

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "cocoamqtt"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-30867.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-30867
# Target: emqx cocoamqtt | CVSS: 5.7 (MEDIUM)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-30867 (emqx cocoamqtt)...")
    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 emqx cocoamqtt 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-2026-30867.sh
# Recommended Remediation & Patching Commands for CVE-2026-30867
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install cocoamqtt 2>/dev/null || \
sudo dnf upgrade cocoamqtt 2>/dev/null || \
sudo yum update cocoamqtt

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

# 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-2026-30867 in emqx cocoamqtt?

Review vendor-specific security notices and update emqx cocoamqtt 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-2026-30867?

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-2026-30867?

CVE-2026-30867 is classified with a CVSS 3.1 Base Score of 5.7 (MEDIUM). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
5.7
MEDIUM SEVERITY
CVE ID CVE-2026-30867
Weakness CWE-617
Vendor emqx
Product cocoamqtt
Published 2026-04-02
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H