CVE-2026-3970: Tenda i3 Buffer Overflow Vulnerability

CVE-2026-3970 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda i3 firmware version 1.0.0.6(2204). The vulnerability exists in the formwrlSSIDget function within the /goform/wifiSSIDget endpoint. When the index argument is manipulated with specially crafted input, it can trigger a stack-based buffer overflow condition. This vulnerability can be exploited remotely over the network, potentially allowing attackers to execute arbitrary code or cause denial of service on affected devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially achieve code execution or crash the device, compromising network infrastructure security.

Affected Products

• Tenda i3 Firmware Version 1.0.0.6(2204)

Discovery Timeline

• March 12, 2026 - CVE-2026-3970 published to NVD
• March 12, 2026 - Last updated in NVD database

Technical Details for CVE-2026-3970

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which encompasses various memory safety issues including buffer overflows. The flaw resides in the web management interface of the Tenda i3 router, specifically within the formwrlSSIDget function that handles WiFi SSID retrieval requests.

The vulnerability can be triggered remotely without user interaction, requiring only low-level privileges to exploit. When successfully exploited, an attacker could potentially achieve full compromise of the affected device, impacting confidentiality, integrity, and availability of the system.

A proof-of-concept exploit has been published and is publicly available, indicating that exploitation techniques are documented and accessible to potential attackers.

Root Cause

The root cause of this vulnerability is improper bounds checking when processing the index parameter in the formwrlSSIDget function. The function fails to properly validate the length or content of user-supplied input before copying it to a fixed-size stack buffer. This allows an attacker to supply an oversized or malformed index value that exceeds the allocated buffer space, causing adjacent memory on the stack to be overwritten.

Attack Vector

The attack is network-based and targets the /goform/wifiSSIDget endpoint on the device's web management interface. An attacker with network access to the vulnerable router can send crafted HTTP requests containing a malicious index parameter value. The exploitation requires low privileges, suggesting that basic authentication may be needed to access the vulnerable endpoint, but no user interaction is required for the attack to succeed.

The attacker crafts a request to the vulnerable endpoint with an oversized index parameter. When the formwrlSSIDget function processes this input, the stack buffer overflows, potentially allowing the attacker to overwrite the return address and redirect execution flow. For detailed technical analysis, refer to the GitHub PoC Repository.

Detection Methods for CVE-2026-3970

Indicators of Compromise

• Unusual or malformed HTTP requests to /goform/wifiSSIDget with abnormally long index parameter values
• Unexpected device reboots or crashes that may indicate exploitation attempts
• Anomalous network traffic patterns targeting the router's web management interface
• Evidence of unauthorized access or configuration changes on Tenda i3 devices

Detection Strategies

• Implement network intrusion detection rules to identify requests with oversized parameters to Tenda router endpoints
• Monitor HTTP traffic to /goform/wifiSSIDget for suspicious payload patterns characteristic of buffer overflow attempts
• Deploy web application firewall rules to block requests with excessively long parameter values targeting Tenda devices
• Establish baseline network behavior for IoT devices and alert on deviations

Monitoring Recommendations

• Enable logging on network security devices to capture traffic to and from Tenda i3 routers
• Implement SIEM correlation rules to detect patterns of exploitation attempts across multiple devices
• Monitor for firmware integrity changes on affected devices that could indicate post-exploitation activity

How to Mitigate CVE-2026-3970

Immediate Actions Required

• Restrict network access to the Tenda i3 web management interface to trusted IP addresses only
• Place affected devices behind a firewall and disable remote management from untrusted networks
• Monitor for vendor security updates and apply patches as soon as they become available
• Consider network segmentation to isolate IoT devices from critical network assets

Patch Information

At the time of publication, no official patch has been released by Tenda. Users should monitor the Tenda Official Website for firmware updates addressing this vulnerability. Additional vulnerability details are available through the VulDB entry.

Workarounds

• Disable the web management interface if not required for device administration
• Implement strict access control lists (ACLs) to limit access to the management interface to specific trusted hosts
• Use a VPN for remote administration rather than exposing the management interface directly
• Consider replacing vulnerable devices with alternative hardware if no patch is forthcoming

# Example firewall rule to restrict access to Tenda management interface
# Replace 192.168.1.1 with your router IP and 192.168.1.100 with trusted admin IP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP