CVE-2023-44018 - Unpacking the Tenda AC10U v1. Stack Overflow Vulnerability

In late 2023, security researchers discovered a critical *stack overflow vulnerability* in the Tenda AC10U v1. wireless router. Officially recognized as CVE-2023-44018, this flaw affects routers running firmware version US_AC10UV1.RTL_V15.03.06.49_multi_TDE01. The vulnerability lies in how the router handles the domain parameter in its add_white_node function—a discovery with potentially serious consequences for users.

This article explains the vulnerability, walks through how it works (with example code), and explores how attackers can exploit it. We’ll also provide links to original sources and advice on mitigation.

What is CVE-2023-44018?

CVE-2023-44018 is a stack buffer overflow vulnerability triggered by improper bounds-checking on user-supplied input to the router's web interface. In plain English, when a user adds a device or domain to the router's whitelist feature, the software doesn't properly check the length of the domain field, allowing an attacker to crash the router—or even run their own code on it.

Where is the Vulnerability?

Specifically, the problem occurs in the /goform/addWhiteNode endpoint. The function add_white_node doesn't properly verify the length of the domain input from a POST request, which can lead to a stack overflow (and potentially arbitrary code execution).

Vulnerable Code Snippet

While Tenda doesn’t provide source code, researchers decompiled the firmware to find the dangerous bit. Here’s a generic pseudocode example that mirrors the vulnerable logic:

void add_white_node(web_request *req) {
    char buf[128];
    char *domain = web_get_param(req, "domain");

    // Problem: No length check here!
    strcpy(buf, domain);

    // Use buf somewhere...
}

The strcpy() function copies the value of domain directly into a fixed-size buffer (buf), but does not check if it will fit. If domain is longer than 128 bytes, it will overflow, overwriting memory in the stack.

How Can Attackers Exploit This Vulnerability?

An attacker can craft a special HTTP POST request with a long 'domain' field that exceeds the buffer size. If successful, the overflow can crash the router or, with skillful payload crafting, let the attacker hijack execution flow—potentially gaining remote code execution.

Here is a simple proof-of-concept request using curl

curl -X POST http://<router_ip>/goform/addWhiteNode \
    -d "domain=$(python -c 'print("A"*200)')&other_param=value"

Replace <router_ip> with the local IP address of your router.

This sends a domain value with 200 A's, much more than the expected 128 bytes, triggering the overflow.

Denial of Service (DoS): The router may reboot or become unresponsive.

- Remote Code Execution (RCE): With careful construction, an attacker could run code of their choice as root.

References and Details

- National Vulnerability Database: CVE-2023-44018
- Security researcher disclosure: Exploit Database 52390
- Firmware Download (archived)
- Vendor Advisory
- Firmware analysis methodology

What Should You Do?

- Update Firmware: Check Tenda's official downloads for the latest firmware. If a patch is not available, contact Tenda support.

Restrict Access: Keep your router’s web management interface inaccessible from the Internet.

- Monitor for Patches: Tenda may release a firmware update to close this hole. Subscribe to CVE update feeds or check the vendor website regularly.

Final Thoughts

CVE-2023-44018 is a reminder of the importance of secure coding and robust validation when handling user inputs, especially in network devices. If you use a Tenda AC10U v1. router, act immediately: update firmware and lock down administrative access. This simple flaw could otherwise open the door for attackers to hijack your network.

Stay safe!

*Exclusive content adapted for real-world understanding. Always reference original advisories and test safely on isolated devices.*

Timeline

Published on: 09/27/2023 15:19:35 UTC
Last modified on: 09/27/2023 18:45:19 UTC