CVE-2026-5046: Tenda FH1201 Buffer Overflow Vulnerability

CVE-2026-5046 Overview

A stack-based buffer overflow vulnerability has been discovered in Tenda FH1201 router firmware version 1.2.0.14(408). The vulnerability exists within the formWrlExtraSet function located in the /goform/WrlExtraSet endpoint of the Parameter Handler component. By manipulating the GO argument, an attacker can trigger a stack-based buffer overflow condition. This vulnerability can be exploited remotely, and an exploit has been publicly disclosed.

Critical Impact

Remote attackers with low-level privileges can exploit this buffer overflow to potentially achieve arbitrary code execution on the affected Tenda FH1201 routers, leading to complete device compromise.

Affected Products

• Tenda FH1201 Firmware version 1.2.0.14(408)
• Tenda FH1201 Hardware

Discovery Timeline

• 2026-03-29 - CVE CVE-2026-5046 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2026-5046

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the formWrlExtraSet function, which handles wireless configuration parameters through the web interface endpoint /goform/WrlExtraSet. The function fails to properly validate the length of user-supplied input passed via the GO argument before copying it into a fixed-size stack buffer.

When an attacker sends a specially crafted HTTP request with an oversized GO parameter value, the function writes beyond the allocated buffer boundaries on the stack. This memory corruption can overwrite critical stack data including saved return addresses and other control structures, potentially allowing an attacker to redirect program execution flow.

The vulnerability is remotely exploitable over the network and requires only low-level privileges to trigger. No user interaction is required for exploitation. Successful exploitation can result in high impact to confidentiality, integrity, and availability of the affected device.

Root Cause

The root cause of this vulnerability is insufficient input validation and improper bounds checking in the formWrlExtraSet function. The code fails to verify that the length of the GO parameter does not exceed the size of the destination buffer before performing the copy operation. This lack of boundary enforcement is a common vulnerability pattern in embedded device firmware where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack can be executed remotely via the network interface of the Tenda FH1201 router. An attacker with network access to the device's web management interface can send a malicious HTTP POST request to the /goform/WrlExtraSet endpoint. By including an oversized value in the GO parameter, the attacker triggers the buffer overflow condition.

The exploitation requires low-level privileges, suggesting the attacker needs some form of authentication to the device, but the attack does not require user interaction beyond the initial access. The vulnerability allows for potential remote code execution, enabling an attacker to gain control of the router, intercept network traffic, modify router configurations, or use the compromised device as a pivot point for further attacks on the network.

For detailed technical analysis and proof-of-concept information, refer to the GitHub README for Vulnerability and the VulDB #353969 entry.

Detection Methods for CVE-2026-5046

Indicators of Compromise

• Unusual HTTP POST requests to /goform/WrlExtraSet with abnormally large GO parameter values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Unexpected changes to wireless configuration settings
• Suspicious network traffic originating from the router to external destinations

Detection Strategies

• Deploy network intrusion detection rules to identify HTTP requests to /goform/WrlExtraSet containing oversized parameter values
• Monitor router logs for unexpected service crashes or restarts of the web server process
• Implement web application firewall rules to block requests with excessively long parameter values to the affected endpoint
• Use firmware integrity monitoring to detect unauthorized modifications to the router's firmware

Monitoring Recommendations

• Enable comprehensive logging on network devices monitoring traffic to and from the Tenda FH1201 router
• Configure alerts for repeated authentication attempts or suspicious access patterns to the router's management interface
• Regularly review router configuration for unauthorized changes
• Monitor for unusual outbound connections from the router that may indicate compromise

How to Mitigate CVE-2026-5046

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management access if not required for operations
• Place the router behind a firewall that can filter malicious requests to the vulnerable endpoint
• Consider replacing the affected device with a router that receives regular security updates

Patch Information

At the time of this publication, no vendor patch has been released for this vulnerability. Users should monitor the Tenda Official Website for firmware updates. Given that the exploit has been publicly disclosed, applying patches promptly upon release is critical.

Additional technical details and vulnerability tracking can be found at VulDB Submission #779127 and the VulDB CTI for #353969.

Workarounds

• Implement access control lists (ACLs) to restrict which IP addresses can access the router's web management interface
• Use a VPN to access the router's management interface rather than exposing it directly to untrusted networks
• Disable the web management interface entirely if alternative configuration methods (such as serial console) are available
• Segment the network to isolate the vulnerable router from sensitive systems and data

# Network segmentation example - block external access to management interface
# Add firewall rule to restrict access to router management port (example using iptables)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP