CVE-2026-3971: Tenda i3 Buffer Overflow Vulnerability

CVE-2026-3971 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda i3 wireless access point, specifically in firmware version 1.0.0.6(2204). The vulnerability exists in the formwrlSSIDset function located in the /goform/wifiSSIDset file, where improper handling of the index and GO arguments allows attackers to overflow the stack buffer. This memory corruption vulnerability can be exploited remotely over the network, potentially allowing attackers to execute arbitrary code or crash the device. The exploit has been publicly disclosed, increasing the risk of active exploitation against vulnerable devices.

Critical Impact

Remote attackers with low-privilege access can exploit this stack-based buffer overflow to achieve arbitrary code execution or denial of service on Tenda i3 wireless access points running vulnerable firmware.

Affected Products

• Tenda i3 Firmware version 1.0.0.6(2204)

Discovery Timeline

• March 12, 2026 - CVE-2026-3971 published to NVD
• March 12, 2026 - Last updated in NVD database

Technical Details for CVE-2026-3971

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), a fundamental memory safety issue that allows attackers to write data beyond the intended boundaries of a buffer. The vulnerable function formwrlSSIDset processes user-supplied input through the index and GO parameters without adequate bounds checking, enabling stack-based buffer overflow conditions.

The network-accessible nature of the vulnerable endpoint (/goform/wifiSSIDset) means that any attacker with network access to the device's management interface can potentially trigger this vulnerability. The attack requires low privileges to execute, making it accessible to authenticated users or attackers who have obtained basic credentials. Successful exploitation could result in complete compromise of the device's confidentiality, integrity, and availability.

Root Cause

The root cause of this vulnerability stems from insufficient input validation within the formwrlSSIDset function. When processing the index or GO arguments from incoming requests to /goform/wifiSSIDset, the function fails to properly validate the length of user-supplied data before copying it into a fixed-size stack buffer. This classic memory corruption pattern allows an attacker to overflow the buffer and overwrite adjacent stack memory, including return addresses and other critical data structures.

Attack Vector

The attack is executed remotely over the network by sending a specially crafted HTTP request to the /goform/wifiSSIDset endpoint on the Tenda i3 device. The attacker manipulates either the index or GO parameter with an oversized payload, causing the stack buffer to overflow. Depending on the payload construction, this can lead to:

1. Denial of Service - Crashing the web service or entire device
2. Code Execution - Overwriting the return address to redirect execution to attacker-controlled code

The vulnerability is accessible via HTTP requests to the device's management interface, which is typically exposed on the local network. Public proof-of-concept exploits have been disclosed, as documented in the GitHub PoC Repository for the index parameter overflow and the GitHub PoC Repository for the GO parameter overflow.

Detection Methods for CVE-2026-3971

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/wifiSSIDset with abnormally large index or GO parameter values
• Device crashes, reboots, or unresponsive behavior following web interface access
• Anomalous network traffic patterns targeting the Tenda i3 management interface
• Suspicious entries in device logs indicating malformed requests or memory errors

Detection Strategies

• Monitor network traffic for HTTP requests to /goform/wifiSSIDset containing oversized parameter values exceeding normal SSID configuration lengths
• Deploy intrusion detection rules to flag requests with unusually long index or GO parameters
• Implement network segmentation to isolate IoT devices and monitor cross-segment traffic anomalies
• Enable logging on network perimeter devices to capture potential exploitation attempts

Monitoring Recommendations

• Configure network monitoring tools to alert on buffer overflow attack patterns targeting embedded devices
• Establish baseline traffic patterns for Tenda device management interfaces to detect deviations
• Monitor for repeated failed authentication attempts or unusual access patterns to the web interface
• Set up automated alerts for device availability to detect potential DoS conditions resulting from exploitation

How to Mitigate CVE-2026-3971

Immediate Actions Required

• Restrict network access to the Tenda i3 management interface to trusted IP addresses only
• Place Tenda i3 devices behind a firewall that blocks external access to the web management interface
• Disable remote management if not required for operations
• Monitor for firmware updates from Tenda and apply patches when available

Patch Information

No official patch information is currently available from Tenda. Organizations should monitor the Tenda Official Site for security advisories and firmware updates addressing this vulnerability. Additional technical details are available through VulDB #350406.

Workarounds

• Implement network-level access controls to restrict access to the /goform/wifiSSIDset endpoint
• Configure a reverse proxy or web application firewall to filter requests with oversized parameters
• Segment the network to isolate Tenda devices from untrusted network segments
• Consider replacing affected devices with alternatives if patches are not forthcoming

# Example: iptables rules to restrict access to Tenda management interface
# Replace TENDA_IP with the device's IP address
# Replace TRUSTED_IP with your management workstation IP

# Block all external access to the web interface
iptables -A INPUT -d TENDA_IP -p tcp --dport 80 -j DROP
iptables -A INPUT -d TENDA_IP -p tcp --dport 443 -j DROP

# Allow only trusted management IPs
iptables -I INPUT -s TRUSTED_IP -d TENDA_IP -p tcp --dport 80 -j ACCEPT