CVE-2024-33603

Executive Summary

CVE-2024-33603 is an information disclosure vulnerability in the LevelOne WBR-6012 router’s web interface. An unauthenticated attacker can access a verbose system log page, revealing sensitive data such as memory addresses and IP addresses used in login attempts. Because the device relies on IP addresses for authentication, this leakage can facilitate session hijacking. The vulnerability has a CVSS score of 5.3 (Medium) and an EPSS score of 0.0%, indicating low exploitation likelihood in the wild. No official patch exists, and the vendor has not acknowledged the issue.

Supply Chain & Package Security

This vulnerability is not related to any software package manager (NPM, PyPI, Go, Ruby). It affects embedded firmware on a consumer router.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
• Base Score: 5.3 (Medium)
• 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: Low (C:L)
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability allows data leakage but does not directly enable code execution or denial of service. However, combined with the IP-based authentication weakness, it can lead to session hijacking.

Deep Dive & Mechanics

The LevelOne WBR-6012 router exposes a web-based administration interface. The vulnerability lies in an unauthenticated endpoint that serves a verbose system log. This log contains:

• Memory addresses (e.g., kernel pointers, buffer addresses)
• IP addresses of recent login attempts (both successful and failed)
• Timestamps and session identifiers

The router uses the source IP address as a primary authentication factor for web sessions. By obtaining a legitimate user’s IP address from the logs, an attacker can spoof that IP and hijack an active session. The log is accessible without any authentication, making exploitation trivial.

Root Cause: The web server does not enforce access controls on the /cgi-bin/log or similar endpoint, and the application logs sensitive data without sanitization.

Vulnerable vs. Patched Code

No patched firmware exists. The vulnerable code is in the router’s web server binary (likely httpd). Below is a conceptual representation:

Vulnerable (pseudo-code):

void handle_log_request() {
    if (strcmp(method, "GET") == 0 && strcmp(path, "/cgi-bin/log") == 0) {
        // No authentication check
        char *log_data = read_system_log();
        send_response(200, log_data);
    }
}

Patched (hypothetical):

void handle_log_request() {
    if (strcmp(method, "GET") == 0 && strcmp(path, "/cgi-bin/log") == 0) {
        if (!is_authenticated()) {
            send_response(403, "Forbidden");
            return;
        }
        char *log_data = read_system_log();
        // Sanitize sensitive fields
        sanitize_log(log_data);
        send_response(200, log_data);
    }
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target: LevelOne WBR-6012 router with default firmware
• Attacker machine: Any system with network access to the router’s web interface (port 80/443)

Exploitation Steps:

1. Identify the router’s IP (e.g., 192.168.1.1).
2. Access the verbose log endpoint:

   curl http://192.168.1.1/cgi-bin/log
   

3. Parse the response for IP addresses and memory addresses.
4. Use a captured IP address to spoof a session:

   curl -H "X-Forwarded-For: <victim_ip>" http://192.168.1.1/admin
   

Example Output:

[2024-01-15 10:23:45] Login attempt from 192.168.1.100 - FAILED
[2024-01-15 10:23:46] Login attempt from 192.168.1.100 - SUCCESS
Memory: 0x7f8a4b2c

Blue Team

Detection:

• Monitor for requests to /cgi-bin/log from external IPs.
• Alert on repeated access to this endpoint without prior authentication.
• Use network segmentation to isolate the router’s management interface.

Honeypot:

• Deploy a fake router endpoint returning dummy logs to detect scanning.

Indicators of Compromise (IOCs)

• Network:
  • HTTP GET requests to /cgi-bin/log
  • Source IPs scanning for LevelOne routers (Shodan dorks)
• Host:
  • Unusual entries in router logs showing repeated access to /cgi-bin/log
• File:
  • No file-based IOCs (firmware only)

Detection Engineering

YARA Rule

rule CVE_2024_33603_LevelOne_Log_Access {
    meta:
        description = "Detects HTTP requests to the vulnerable log endpoint on LevelOne WBR-6012"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-33603"
    strings:
        $log_path = "/cgi-bin/log"
        $router_header = "LevelOne"
    condition:
        $log_path and $router_header
}

Sigma Rule

title: LevelOne WBR-6012 Verbose Log Access
id: 7a8b3c4d-5e6f-7890-abcd-ef1234567890
status: experimental
description: Detects unauthenticated access to the verbose system log on LevelOne WBR-6012 routers
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-path: "/cgi-bin/log"
        cs-method: "GET"
    condition: selection
falsepositives:
    - Legitimate admin troubleshooting
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-33603 LevelOne WBR-6012 Verbose Log Access"; flow:to_server; http.method; content:"GET"; http.uri; content:"/cgi-bin/log"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable remote web management if not required.
2. Restrict access to the router’s web interface to trusted IPs only.
3. Use a VPN to access the management interface.

Long-Term:

• Replace the router with a patched or supported model.
• Monitor vendor for firmware updates (unlikely).
• Implement network segmentation to isolate IoT devices.

Workaround:

• Block access to /cgi-bin/log via a reverse proxy or firewall rule.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert