CVE-2025-3802: Critical Vulnerability in Tenda Wifi Routers

Overview

In this post, we will delve into a critical vulnerability (CVE-2025-3802) that affects Tenda W12 and i24 routers, specifically the versions 3.0.0.4(2887) and 3.0.0.5(3644). The susceptibility was located in the function cgiPingSet of the file /bin/httpd. This vulnerability matters because the exploitation of this flaw can lead to a stack-based buffer overflow, which can potentially compromise the system or lead to data leakage. Being remote, this vulnerability poses significant risks to all Tenda W12 and i24 users worldwide.

Vulnerability Summary

CVE ID: CVE-2025-3802
Severity: Critical, CVSS Score – 8.8
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise and data leakage

Affected Products

Product | Affected Versions

Tenda W12 | 3.0.0.4(2887) and 3.0.0.5(3644)
Tenda i24 | 3.0.0.4(2887) and 3.0.0.5(3644)

How the Exploit Works

The vulnerability lies within the cgiPingSet function of the /bin/httpd file. It is triggered by manipulating the pingIP argument that leads to a stack-based buffer overflow. A buffer overflow occurs when more data is written to a buffer than it can handle, causing it to overflow. This overflow can overwrite adjacent memory locations, leading to erratic program behavior, including memory access errors, incorrect results, and crashes.
In this case, the buffer overflow can be exploited remotely without any user interaction, making it a significant threat. Successful exploitation can lead to unauthorized disclosure of information, unauthorized modification, and even disruption of service.

Conceptual Example Code

Here’s a conceptual example of a malicious HTTP request that could exploit this vulnerability:

POST /cgi-bin/cgiPingSet HTTP/1.1
Host: [target IP]
Content-Type: application/x-www-form-urlencoded
pingIP=192.168.0.1%00 [Additional malicious payload]

In this example, the attacker sends a POST request to the cgiPingSet endpoint, using a manipulated pingIP argument. The address `192.168.0.1%00` is a null byte that terminates the string and is followed by the excess data (malicious payload) that causes the buffer to overflow.

Remediation

The recommended mitigation strategy is to apply the patch provided by the vendor. If not possible immediately, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can offer temporary mitigation. However, it is advised to apply the patch as soon as possible to prevent potential system compromise or data leakage.