CVE-2026-4007: Tenda W3 Buffer Overflow Vulnerability

CVE-2026-4007 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda W3 routers running firmware version 1.0.0.3(2204). This vulnerability exists in the /goform/wifiSSIDget endpoint within the POST Parameter Handler component. By manipulating the index argument, remote attackers can trigger a buffer overflow condition that may lead to arbitrary code execution or denial of service on affected devices.

Critical Impact

Remote attackers with low privileges can exploit this stack-based buffer overflow to potentially execute arbitrary code or crash the device, compromising network security and availability.

Affected Products

• Tenda W3 Router Firmware Version 1.0.0.3(2204)

Discovery Timeline

• 2026-03-12 - CVE-2026-4007 published to NVD
• 2026-03-12 - Last updated in NVD database

Technical Details for CVE-2026-4007

Vulnerability Analysis

This vulnerability is classified as a stack-based buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the web management interface of the Tenda W3 router, specifically within the POST parameter handling code for the /goform/wifiSSIDget endpoint.

When the router processes HTTP POST requests to this endpoint, insufficient bounds checking is performed on the index parameter before copying data to a fixed-size stack buffer. This lack of proper input validation allows an attacker to submit a maliciously crafted request containing an oversized index value that exceeds the allocated buffer space, corrupting adjacent stack memory including return addresses and saved registers.

The vulnerability is remotely exploitable over the network and requires only low-privilege authentication to trigger. An attacker positioned on the same network segment or with access to the router's management interface can send specially crafted HTTP requests to exploit this flaw. A public proof-of-concept exploit has been made available, increasing the likelihood of exploitation in the wild.

Root Cause

The root cause of this vulnerability is improper input validation and bounds checking in the POST parameter handler code. When processing the index argument in requests to /goform/wifiSSIDget, the firmware fails to verify that the input length does not exceed the size of the destination stack buffer before performing memory copy operations. This allows attackers to write data beyond the buffer boundary, corrupting the stack and potentially hijacking program execution flow.

Attack Vector

The attack vector for CVE-2026-4007 is network-based. An attacker can exploit this vulnerability by sending a specially crafted HTTP POST request to the /goform/wifiSSIDget endpoint with a maliciously constructed index parameter. The attack requires low-privilege access to the router's web management interface but does not require user interaction.

The exploitation process involves:

1. Identifying a vulnerable Tenda W3 router with firmware version 1.0.0.3(2204)
2. Crafting an HTTP POST request targeting the /goform/wifiSSIDget endpoint
3. Including an oversized index parameter designed to overflow the stack buffer
4. Sending the request to overwrite return addresses and gain control of execution flow

For technical details on the exploitation mechanism, refer to the GitHub PoC Repository.

Detection Methods for CVE-2026-4007

Indicators of Compromise

• Unusual HTTP POST requests to /goform/wifiSSIDget with abnormally large index parameter values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Unexpected network traffic patterns originating from the router's management interface
• Evidence of unauthorized configuration changes on the affected device

Detection Strategies

• Monitor web server logs for requests to /goform/wifiSSIDget containing oversized parameter values
• Implement intrusion detection signatures to identify stack overflow exploitation patterns targeting Tenda devices
• Deploy network-based anomaly detection to flag unusual HTTP request sizes to router management endpoints
• Review firmware versions on all Tenda W3 devices to identify vulnerable installations

Monitoring Recommendations

• Enable logging on network firewalls and WAF devices for traffic to router management interfaces
• Configure alerts for repeated failed requests or crash conditions on Tenda W3 routers
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Regularly audit device firmware versions against known vulnerable releases

How to Mitigate CVE-2026-4007

Immediate Actions Required

• Restrict access to the router's web management interface to trusted networks and administrators only
• Implement network segmentation to prevent unauthorized access to router management endpoints
• Monitor the Tenda Official Website for security updates and firmware patches
• Consider replacing vulnerable devices if no patch becomes available

Patch Information

At the time of publication, no official patch from Tenda has been confirmed for this vulnerability. Organizations should monitor vendor security advisories for updates. Additional technical details and threat intelligence are available through VulDB CTI #350530.

Workarounds

• Disable remote management access to the router's web interface if not required
• Implement firewall rules to block external access to the /goform/wifiSSIDget endpoint
• Use VPN or jump hosts for administrative access to router management interfaces
• Deploy a web application firewall (WAF) with rules to detect and block buffer overflow attempts

# Example iptables rule to restrict access to router management interface
# Replace 192.168.1.0/24 with your trusted management network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP