CVE-2026-7034: Tenda FH1202 Buffer Overflow Vulnerability

CVE-2026-7034 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda FH1202 wireless router firmware version 1.2.0.14(408). The vulnerability exists in the WrlExtraSet function within the /goform/WrlExtraSet endpoint of the httpd component. Attackers can exploit this vulnerability by manipulating the Go argument, leading to a stack-based buffer overflow condition that can be triggered remotely.

Critical Impact
Remote attackers with low privileges can exploit this buffer overflow to potentially execute arbitrary code, compromise device integrity, or cause denial of service on affected Tenda FH1202 routers.

Affected Products

Tenda FH1202 Firmware version 1.2.0.14(408)
Tenda FH1202 Hardware device

Discovery Timeline

2026-04-26 - CVE-2026-7034 published to NVD
2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7034

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 WrlExtraSet function in the Tenda FH1202 router's httpd service fails to properly validate the length of user-supplied input passed through the Go parameter. When an attacker sends a specially crafted HTTP request to the /goform/WrlExtraSet endpoint with an oversized Go argument, the function writes data beyond the allocated stack buffer boundaries.

The vulnerability can be exploited remotely over the network without requiring user interaction. An authenticated attacker with low privileges can trigger the overflow, potentially overwriting critical stack data including return addresses and saved registers. This could enable arbitrary code execution with the privileges of the httpd process, typically running as root on embedded devices like consumer routers.

Root Cause

The root cause of this vulnerability is insufficient bounds checking on user-controlled input in the WrlExtraSet function. The firmware does not properly validate or sanitize the length of the Go argument before copying it to a fixed-size stack buffer. This lack of input validation allows attackers to overflow the buffer and corrupt adjacent memory on the stack.

Attack Vector

The attack is conducted remotely over the network through the router's web management interface. An attacker sends a malicious HTTP POST request to the /goform/WrlExtraSet endpoint containing an oversized Go parameter value. The attack requires low-level authentication but no user interaction, making it exploitable by any authenticated user or attacker who has obtained valid credentials.

The vulnerability is accessible through the httpd component that handles web-based administration requests. Successful exploitation could result in complete compromise of the router, allowing attackers to modify device configurations, intercept network traffic, or use the device as a pivot point for further attacks on the internal network.

Technical details and proof-of-concept information are available in the GitHub PoC Repository and VulDB entry #359614.

Detection Methods for CVE-2026-7034

Indicators of Compromise

Anomalous HTTP POST requests to /goform/WrlExtraSet with unusually large Go parameter values
Unexpected crashes or restarts of the httpd service on Tenda FH1202 devices
Abnormal network traffic patterns originating from the router's management interface
Unauthorized configuration changes or firmware modifications on affected devices

Detection Strategies

Monitor HTTP traffic to /goform/WrlExtraSet endpoints for requests containing oversized parameters exceeding normal operational bounds
Implement network intrusion detection rules to identify buffer overflow exploitation patterns targeting Tenda router endpoints
Review access logs on network perimeter devices for connections to known vulnerable firmware management interfaces
Deploy network segmentation to isolate IoT devices and enable focused monitoring of router management traffic

Monitoring Recommendations

Enable logging on all network boundary devices to capture traffic destined for router management ports
Configure SIEM rules to alert on multiple failed authentication attempts followed by successful access to router administration interfaces
Monitor for unexpected outbound connections from router IP addresses that may indicate post-exploitation activity
Regularly audit firmware versions across all Tenda devices to identify vulnerable deployments

How to Mitigate CVE-2026-7034

Immediate Actions Required

Restrict network access to the router's web management interface to trusted internal IP addresses only
Disable remote management functionality if not operationally required
Implement network segmentation to isolate vulnerable devices from critical network segments
Monitor the Tenda Official Website for security updates and firmware patches

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations using affected Tenda FH1202 devices with firmware version 1.2.0.14(408) should monitor vendor communications for security updates. Additional technical information is available through VulDB Submission #798476.

Workarounds

Configure firewall rules to block external access to the router's web management interface on ports 80 and 443
Enable access control lists (ACLs) to limit management interface access to specific trusted IP addresses
Consider replacing affected devices with actively supported alternatives if no patch becomes available
Implement a web application firewall (WAF) in front of management interfaces to filter malicious requests

bash

# Example iptables rules to restrict management interface access
# Allow management access only from trusted admin subnet
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
# Drop all other external management access
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP