In late 2022, a serious security issue known as CVE-2022-44807 was discovered affecting certain models of D-Link routers, specifically D-Link DIR-882 firmware versions 1.10B02 and 1.20B06. This vulnerability is caused by a buffer overflow in the router's web interface and can allow an attacker to gain control of the device. In this post, we break down the details of the issue, provide code examples, and explain how attackers can exploit it.

What’s the Issue?

A buffer overflow occurs when a program writes more data to a buffer than it can handle, overwriting adjacent memory. If exploited properly, this can allow attackers to run arbitrary code leading to remote code execution (RCE) or denial of service (DoS).

The dangerous part? This flaw can be triggered by a normal HTTP request to the device’s web interface, specifically through improper handling in a function called webGetVarString.

How Does It Work?

The D-Link DIR-882 web interface uses a custom function called webGetVarString to handle HTTP GET/POST variables sent to the router. In affected firmware versions, this function doesn’t check the length of the input data. If a specially crafted input string (that’s too long) is sent to this function, it overflows the buffer’s boundaries.

This means a hacker can send a long enough string via the web interface and crash the router or execute malicious code.

Code Sample

Here’s a simplified C-like example based on public research and reverse engineering (peace of mind, this is not the actual code, but very similar):

int webGetVarString(char *input, char *output) {
    char buffer[128];  // buffer with fixed size
    strcpy(buffer, input);  // No size check!
    strcpy(output, buffer);
    return ;
}

Notice the use of strcpy, which copies strings without checking length. A long input can overwrite important parts of memory.

Proof-of-Concept Exploit (PoC)

To show how simple the attack is, here’s a Python script that sends an excessively long string to the vulnerable router:

import requests

# Change this to your DIR-882's IP address
router_ip = "192.168..1"

# Long payload to trigger the overflow
payload = "A" * 500

url = f"http://{router_ip}/some_endpoint.cgi?var={payload}";

try:
    response = requests.get(url, timeout=5)
    print(f"HTTP Status: {response.status_code}")
except Exception as e:
    print(f"Request failed: {e}")

If crafted with advanced payload, an attacker could run code on the device with admin rights.

Note: Do NOT run this script on devices you don’t own or have permission to test.

Exploit Details

- CVE Identifier: CVE-2022-44807

Crash the router: Make it reboot or freeze, knocking users offline.

2. Potentially execute code: Gain full control of the router, eavesdrop network traffic, or attack connected devices.

- CVE-2022-44807 on NVD (Official Details)
- Exploit Database Reference  
- D-Link Security Advisories

Mitigation: How to Stay Safe

- Update Firmware: D-Link usually releases patches. Check D-Link support for the latest firmware for your DIR-882 router.

Conclusion

CVE-2022-44807 is a great example of how unsafe coding practices, like unchecked buffer use, can have big consequences. Always keep your devices updated and practice good security hygiene to protect yourself from such threats.

If you have a D-Link DIR-882, make sure to check for updates or consider replacing the router if it can’t be secured.


Original research and exclusive insights by AI. For more details and responsible disclosure, review the official CVE and vendor bulletins. Stay safe online!

Timeline

Published on: 11/22/2022 15:15:00 UTC
Last modified on: 11/23/2022 19:53:00 UTC