CVE-2026-5045: Tenda FH1201 Buffer Overflow Vulnerability

CVE-2026-5045 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda FH1201 router firmware version 1.2.0.14(408). The vulnerability exists in the WrlclientSet function within the /goform/WrlclientSet endpoint of the Parameter Handler component. An attacker can exploit this flaw by manipulating the GO argument, leading to a stack-based buffer overflow condition that can be triggered remotely over the network.

Critical Impact

Remote attackers with low privileges can exploit this buffer overflow to potentially achieve code execution on affected Tenda FH1201 routers, compromising network security and device integrity.

Affected Products

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

Discovery Timeline

• 2026-03-29 - CVE-2026-5045 published to NVD
• 2026-03-30 - Last updated in NVD database

Technical Details for CVE-2026-5045

Vulnerability Analysis

This vulnerability affects the WrlclientSet function in the Tenda FH1201 router's web management interface. The affected endpoint /goform/WrlclientSet fails to properly validate the length of user-supplied input passed through the GO parameter before copying it into a fixed-size stack buffer. When an attacker sends a specially crafted HTTP request with an oversized GO argument, the function writes beyond the allocated buffer boundaries on the stack.

Stack-based buffer overflows in embedded devices like routers are particularly concerning because these devices often lack modern memory protection mechanisms such as ASLR (Address Space Layout Randomization) or stack canaries. This makes exploitation more reliable and increases the likelihood of successful code execution. The network-accessible nature of this vulnerability means attackers can trigger it remotely without physical access to the device.

Root Cause

The root cause is improper bounds checking in the WrlclientSet function (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The function does not validate the length of the GO parameter before copying the input data into a stack-allocated buffer, allowing memory corruption when oversized input is provided.

Attack Vector

The attack can be carried out remotely over the network. An authenticated attacker with low privileges can send a malicious HTTP request to the /goform/WrlclientSet endpoint with a crafted GO parameter containing excess data. The overflow occurs when this data exceeds the expected buffer size, potentially overwriting the return address and other critical stack data.

The vulnerability is exploitable by sending HTTP POST requests to the device's web interface. The exploit has been publicly disclosed, and technical details are available through the GitHub Vulnerability Documentation. Additional vulnerability information can be found in the VulDB Vulnerability Details.

Detection Methods for CVE-2026-5045

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/WrlclientSet with unusually large GO parameter values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Anomalous network traffic patterns originating from or directed at Tenda FH1201 devices
• Unusual processes or services running on the router if code execution was achieved

Detection Strategies

• Monitor HTTP traffic to Tenda FH1201 devices for POST requests to /goform/WrlclientSet with oversized parameters
• Implement network intrusion detection rules to flag requests with GO parameter lengths exceeding normal operational limits
• Deploy web application firewall (WAF) rules to inspect and block malformed requests targeting the vulnerable endpoint
• Utilize SentinelOne Singularity for network visibility and threat detection across IoT and embedded devices

Monitoring Recommendations

• Enable logging on network perimeter devices to capture traffic to/from Tenda routers
• Implement anomaly detection for HTTP request sizes targeting router management interfaces
• Regularly review router access logs for suspicious activity patterns
• Configure alerts for router availability issues that may indicate exploitation attempts

How to Mitigate CVE-2026-5045

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management features if not required for operations
• Place affected Tenda FH1201 devices behind a firewall with strict ingress filtering
• Monitor for firmware updates from Tenda and apply patches when available

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for security advisories and firmware updates. Consider upgrading to alternative hardware if patches are not forthcoming and the device is exposed to untrusted networks.

Workarounds

• Disable the web management interface entirely and manage the device through serial console if possible
• Implement network segmentation to isolate affected routers from critical network resources
• Use access control lists (ACLs) to limit which hosts can reach the management interface
• Consider replacing vulnerable devices with alternatives that have active security support

# Example: Restrict management interface access using upstream firewall
# Block external access to router management ports
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -j DROP
# Allow management only from trusted admin workstation
iptables -I FORWARD -s <ADMIN_IP> -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT