CVE-2025-67446

Executive Summary

CVE-2025-67446 is a critical Improper Authentication vulnerability in the Neterbit NW-431F router, affecting firmware version 20241014-IR03 and all prior releases. The flaw allows an unauthenticated, remote attacker to bypass the router's authentication mechanism by simply modifying a cookie value (e.g., setting it to "admin"). This grants full administrative access to the device's web interface, enabling complete control over network traffic, firewall rules, and connected devices.

The vulnerability has a CVSS score of 9.8 (Critical) due to its low attack complexity, no required privileges, and no user interaction. No public exploit code or Nuclei template is currently available, but the attack vector is trivial to implement. No patch has been released by Neterbit, leaving all affected devices exposed.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level authentication bypass in an embedded device.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 9.8 (Critical)
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – no prior authentication needed.
• User Interaction: None (UI:N) – no victim action required.
• Scope: Unchanged (S:U) – the vulnerable component is the only affected component.
• Confidentiality Impact: High (C:H) – full read access to device configuration and network data.
• Integrity Impact: High (I:H) – ability to modify firmware, routing, and firewall rules.
• Availability Impact: High (A:H) – can disable the device or disrupt network connectivity.

Threat Level: Critical. The attack is trivial to execute and requires no specialized tools. An attacker can gain full administrative control over the router, pivot to internal networks, and perform man-in-the-middle attacks.

Deep Dive & Mechanics

The Neterbit NW-431F router uses a cookie-based authentication mechanism for its web administration interface. The vulnerability lies in the server-side validation of the authentication cookie. Instead of using a cryptographically signed or randomly generated session token, the router simply checks if the cookie value matches a hardcoded or predictable string (e.g., "admin"). An attacker can craft an HTTP request with a cookie set to "admin" and gain immediate access to all administrative functions without providing valid credentials.

Root Cause: The router's web server does not verify the authenticity or integrity of the session cookie. It trusts the client-supplied cookie value directly, allowing an attacker to impersonate any user, including the administrator.

Attack Flow:

1. Attacker identifies a Neterbit NW-431F router (e.g., via Shodan or local network scanning).
2. Attacker sends an HTTP GET request to the router's admin interface (e.g., /cgi-bin/admin).
3. The request includes a cookie header: Cookie: admin=admin (or similar).
4. The router's web server processes the cookie and grants full administrative access.
5. Attacker can now modify settings, extract credentials, or deploy malicious firmware.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

# Pseudocode for vulnerable authentication check
def check_authentication(request):
    cookie = request.cookies.get('admin')
    if cookie == 'admin':
        return True  # Grants admin access
    else:
        return False

Patched Code (Conceptual):

# Pseudocode for patched authentication check
import secrets

def check_authentication(request):
    session_token = request.cookies.get('session')
    if session_token and session_token in valid_sessions:
        return True
    else:
        return False

def generate_session():
    return secrets.token_hex(32)

The patched version uses a cryptographically random session token stored server-side, preventing simple cookie manipulation.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Access to a Neterbit NW-431F router (e.g., on a local network or exposed to the internet).
• A tool like curl, Burp Suite, or a web browser with cookie editing capabilities.

Exploitation Steps:

1. Identify the router's IP address (e.g., 192.168.1.1).
2. Send a crafted HTTP request with the malicious cookie:

   curl -b "admin=admin" http://192.168.1.1/cgi-bin/admin
   

3. The router responds with the admin panel, granting full control.

Alternative Method (Browser):

1. Open the router's admin page in a browser.
2. Use developer tools to set a cookie: admin=admin.
3. Refresh the page to access the admin interface.

Blue Team (Detection & Hardening)

Detection:

• Monitor HTTP requests for unusual cookie values (e.g., admin=admin, user=admin).
• Look for repeated failed login attempts followed by a successful request with a cookie set.
• Use network traffic analysis to detect unauthorized access to the admin interface.

Hardening:

• Immediately isolate affected routers from the internet if no patch is available.
• Implement network segmentation to limit exposure.
• Use a reverse proxy with strong authentication in front of the router.
• Monitor for Shodan exposure and request takedown if necessary.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests to /cgi-bin/admin or similar admin endpoints with a cookie containing admin=admin.
• Unusual outbound connections from the router to unknown IPs (e.g., C2 servers).
• Changes to DNS settings or routing tables.

File IOCs:

• Modified firmware files or configuration backups.
• Presence of unauthorized scripts or binaries in the router's filesystem.

Behavioral IOCs:

• Sudden changes in firewall rules or port forwarding.
• Unexplained reboots or firmware updates.
• New user accounts or modified admin credentials.

Detection Engineering

YARA Rule

rule CVE_2025_67446_AuthBypass {
    meta:
        description = "Detects HTTP requests exploiting CVE-2025-67446 authentication bypass"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-67446"
    strings:
        $cookie = "admin=admin" nocase
        $admin_path = "/cgi-bin/admin" nocase
    condition:
        $cookie and $admin_path
}

Sigma Rule

title: CVE-2025-67446 Neterbit Router Authentication Bypass
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests with admin cookie bypassing authentication on Neterbit NW-431F routers
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-67446
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem: '/cgi-bin/admin'
        cs-cookie: 'admin=admin'
    condition: selection
falsepositives:
    - Legitimate admin access (unlikely with this cookie value)
level: critical

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-67446 Neterbit Router Authentication Bypass"; flow:to_server; content:"GET"; http_method; content:"/cgi-bin/admin"; http_uri; content:"admin=admin"; http_cookie; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable remote administration on the router if not required.
2. Change default credentials and use strong, unique passwords.
3. Apply network segmentation to isolate the router from untrusted networks.
4. Monitor logs for unauthorized access attempts.

Long-Term Fix:

• Vendor Patch: Neterbit must release a firmware update that implements proper session management with cryptographically random tokens.
• Workaround: If no patch is available, replace the router with a secure alternative.

Detection & Response:

• Deploy the provided YARA, Sigma, and Suricata rules to detect exploitation attempts.
• Implement a Web Application Firewall (WAF) rule to block requests with suspicious cookie values.

Valters IT
Securing Digital Frontiers