CVE-2026-4043: Tenda I12 Firmware Buffer Overflow Flaw

CVE-2026-4043 Overview

CVE-2026-4043 is a stack-based buffer overflow vulnerability in the Tenda i12 wireless access point running firmware version 1.0.0.6(2204). The flaw resides in the formwrlSSIDget function within the /goform/wifiSSIDget endpoint. Attackers can trigger the overflow by manipulating the index argument, corrupting the stack frame on the device. The vulnerability is remotely exploitable over the network and requires only low privileges. Public disclosure of exploitation details has occurred, increasing the likelihood of weaponization against exposed devices. The Common Weakness Enumeration (CWE) classifications assigned are [CWE-119] and [CWE-787].

Critical Impact
A remote, authenticated attacker can corrupt stack memory on Tenda i12 devices through the wifiSSIDget endpoint, enabling potential code execution or device compromise on affected firmware.

Affected Products

Tenda i12 hardware device
Tenda i12 firmware version 1.0.0.6(2204)
Web management interface endpoint /goform/wifiSSIDget

Discovery Timeline

2026-03-12 - CVE-2026-4043 published to the National Vulnerability Database (NVD)
2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-4043

Vulnerability Analysis

The vulnerability is a stack-based buffer overflow in the formwrlSSIDget handler that services HTTP requests sent to /goform/wifiSSIDget. This handler is part of the Tenda i12 web administration interface used to retrieve wireless SSID configuration. When the handler processes the index query parameter, it copies the attacker-controlled value into a fixed-size stack buffer without enforcing length boundaries. Overrunning that buffer overwrites adjacent stack memory, including saved return addresses on the MIPS or ARM-based router platform.

Exploitation requires network reachability to the device's HTTP management service and low-level credentials to reach the form handler. Once memory corruption succeeds, an attacker can pivot to arbitrary code execution, persistent device implantation, or denial of service against the access point.

Root Cause

The root cause is unsafe handling of HTTP request parameters inside formwrlSSIDget. The function fails to validate the length of the index argument before copying it into a stack buffer, a recurring pattern in Tenda goform handlers. This pattern maps to [CWE-787] Out-of-bounds Write and [CWE-119] improper restriction of operations within memory bounds.

Attack Vector

An attacker sends a crafted HTTP request to /goform/wifiSSIDget with an oversized index parameter. The request can be issued from any network-adjacent host that can reach the device's HTTP service, including LAN segments and devices that expose management over WAN. The publicly available exploit details lower the technical bar for attackers seeking to weaponize this flaw.

No verified proof-of-concept code has been published in a trusted exploit repository. See the GitHub Issue Discussion and VulDB #350655 for further technical details.

Detection Methods for CVE-2026-4043

Indicators of Compromise

HTTP requests to /goform/wifiSSIDget containing abnormally long index parameter values
Unexpected reboots, crashes, or service restarts on Tenda i12 access points
Outbound connections from the access point to unfamiliar external hosts following inbound HTTP traffic
Unauthorized configuration changes to wireless or routing settings on the device

Detection Strategies

Inspect web access logs and network captures for POST or GET requests targeting /goform/wifiSSIDget with parameter lengths exceeding typical SSID index values
Deploy network intrusion detection signatures matching oversized index parameters destined for Tenda goform endpoints
Baseline normal management traffic to the access point and alert on deviations in request size or frequency

Monitoring Recommendations

Forward router syslog and management interface logs to a centralized analytics platform for correlation
Monitor for repeated HTTP 5xx responses from the device, which may indicate crash conditions during exploitation attempts
Track administrative access to the device and alert on connections from unexpected source addresses

How to Mitigate CVE-2026-4043

Immediate Actions Required

Restrict access to the Tenda i12 web management interface to trusted management VLANs only
Disable remote WAN-side administration if currently enabled on the device
Rotate administrative credentials and enforce strong passwords to limit the low-privilege precondition
Audit network logs for prior requests to /goform/wifiSSIDget containing unusually long parameters

Patch Information

No vendor patch has been referenced in the NVD entry for CVE-2026-4043. Administrators should monitor the Tenda Official Website for firmware updates addressing firmware version 1.0.0.6(2204). Until an official fix is released, treat the device as exposed and apply compensating network controls.

Workarounds

Place the access point behind a firewall that blocks untrusted access to TCP ports used by the management web server
Segment IoT and network infrastructure devices onto a dedicated VLAN with strict egress filtering
Consider replacing the device with a supported model if no patch becomes available for this firmware revision
Disable unnecessary services on the access point to reduce the attack surface

bash

# Example iptables rule to restrict management access to a trusted subnet
iptables -A INPUT -p tcp --dport 80 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.0.2.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP