HIGH CVSS 8.8
Published: 2026-03-26

CVE-2026-4861

wavlink wl-nu516u1_firmware Security Advisory (CVE-2026-4861)
↗ Official NIST NVD Record
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CyberVault Technical Summary

Analyst Synthesis

Technical analysis, exploit verification, and patch instructions for CVE-2026-4861 impacting wavlink wl-nu516u1_firmware. Evaluated with CVSS Base Score of 8.8 (HIGH).

Original NVD Description

Source: NIST NVD
A weakness has been identified in Wavlink WL-NU516U1 260227. This vulnerability affects the function ftext of the file /cgi-bin/nas.cgi. This manipulation of the argument Content-Length causes stack-based buffer overflow. The attack can be initiated remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

📊 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
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 wavlink / wl-nu516u1_firmware
Affected Versions m16u1_v260227
Weakness Enumeration CWE-119

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-2026-4861 impacting wavlink wl-nu516u1_firmware.

⚡ Nuclei Detection Template (YAML) cve-2026-4861.yaml
id: cve-2026-4861

info:
  name: wavlink wl-nu516u1_firmware - Security Advisory & Vulnerability Scan
  author: cybervault-security-intel
  severity: high
  description: |
    Automated signature & scanner for CVE-2026-4861 affecting wavlink wl-nu516u1_firmware.
    Evaluation: A weakness has been identified in Wavlink WL-NU516U1 260227. This vulnerability affects the function ftext of the file /cgi-bin/nas.cgi. This manipula...
  reference:
    - https://cybervault-cve.pages.dev/cve/CVE-2026-4861
  classification:
    cvss-metrics: CVSS:3.1/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 8.8
    cve-id: CVE-2026-4861
    cwe-id: CWE-119
  tags: cve,cve-2026-4861,wavlink,wl-nu516u1_firmware,high

http:
  - method: GET
    path:
      - "{BaseURL}/"
      - "{BaseURL}/api/"
    matchers-condition: and
    matchers:
      - type: status
        status:
          - 200
      - type: word
        words:
          - "wl-nu516u1_firmware"
        part: body
🐍 PoC Exploit & Verification Probe (Python 3) poc_cve-2026-4861.py
# Proof-of-Concept Exploit & Verification Probe for CVE-2026-4861
# Target: wavlink wl-nu516u1_firmware | CVSS: 8.8 (HIGH)
# Educational & Security Audit Purpose Only

import requests
import sys

def verify_vulnerability(target_url):
    print(f"[*] Auditing {target_url} for CVE-2026-4861 (wavlink wl-nu516u1_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 wavlink wl-nu516u1_firmware scope (m16u1_v260227).")
        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-2026-4861.sh
# Recommended Remediation & Patching Commands for CVE-2026-4861
# 1. Update package via distribution package manager:
sudo apt-get update && sudo apt-get --only-upgrade install wl-nu516u1_firmware 2>/dev/null || \
sudo dnf upgrade wl-nu516u1_firmware 2>/dev/null || \
sudo yum update wl-nu516u1_firmware

# 2. Inspect installed package versions for vulnerable scope:
dpkg -l | grep -i wl-nu516u1_firmware 2>/dev/null || rpm -qa | grep -i wl-nu516u1_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.

🔗 Verified Technical References

❓ Frequently Asked Questions (FAQ) & Remediation Guide

How do I fix CVE-2026-4861 in wavlink wl-nu516u1_firmware?

Review vendor-specific security notices and update wavlink wl-nu516u1_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-2026-4861?

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-2026-4861?

CVE-2026-4861 is classified with a CVSS 3.1 Base Score of 8.8 (HIGH). Check the metric breakdown above for attack vector requirements.

Risk Snapshot
8.8
HIGH SEVERITY
CVE ID CVE-2026-4861
Weakness CWE-119
Vendor wavlink
Product wl-nu516u1_firmware
Published 2026-03-26
Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H