CVE-2026-3728: Tenda F453 Buffer Overflow Vulnerability

CVE-2026-3728 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda F453 router firmware version 1.0.0.3. This vulnerability affects the fromSetCfm function within the /goform/setcfm endpoint, where improper handling of the funcname and funcpara1 arguments leads to memory corruption. The vulnerability can be exploited remotely over the network, potentially allowing attackers to execute arbitrary code or cause denial of service on affected devices. The exploit has been publicly disclosed, increasing the risk of exploitation in the wild.

Critical Impact

Remote attackers with low privileges can exploit this stack-based buffer overflow to compromise Tenda F453 routers, potentially gaining full control over the device or disrupting network services.

Affected Products

• Tenda F453 Firmware version 1.0.0.3
• Tenda F453 Hardware Device

Discovery Timeline

• 2026-03-08 - CVE-2026-3728 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-3728

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which represents a fundamental memory safety issue in the Tenda F453 firmware. The fromSetCfm function fails to properly validate the length of user-supplied input through the funcname and funcpara1 parameters before copying data to stack-allocated buffers.

When an attacker sends a specially crafted HTTP request to the /goform/setcfm endpoint with oversized input values, the function writes data beyond the allocated buffer boundaries on the stack. This memory corruption can overwrite critical stack structures including saved return addresses and stack canaries (if present), enabling control flow hijacking.

The network-accessible nature of this vulnerability significantly increases its severity. Authenticated attackers with low-level access can remotely trigger the overflow without requiring physical access to the device. Given that router devices often serve as network gateways, successful exploitation could compromise the entire network infrastructure.

Root Cause

The root cause of this vulnerability lies in the absence of proper input length validation within the fromSetCfm function. The function directly processes user-controlled input from the funcname and funcpara1 HTTP parameters without verifying that the input size does not exceed the allocated buffer capacity. This lack of bounds checking is a common issue in embedded device firmware where memory-safe programming practices may not be consistently applied.

Attack Vector

The attack is conducted remotely over the network by sending malicious HTTP POST requests to the vulnerable /goform/setcfm endpoint. An attacker with low-privilege network access can craft requests containing oversized funcname or funcpara1 parameter values designed to overflow the stack buffer.

The exploitation flow involves sending crafted HTTP requests to overflow stack memory, corrupting the function's return address with attacker-controlled values. If successful, this redirects execution to attacker-specified code or existing code gadgets within the firmware. Technical details and proof-of-concept information are available in the GitHub Vulnerability Repository.

Detection Methods for CVE-2026-3728

Indicators of Compromise

• Unusual or malformed HTTP POST requests to /goform/setcfm endpoint with abnormally large parameter values
• Unexpected router crashes, reboots, or service interruptions without administrative action
• Anomalous outbound network connections originating from the router device
• Changes to router configuration or settings without authorized modifications

Detection Strategies

• Deploy network intrusion detection systems (IDS) with rules to monitor for oversized HTTP POST requests targeting /goform/setcfm
• Implement web application firewall (WAF) rules to block requests with excessively long funcname or funcpara1 parameters
• Monitor router system logs for crash dumps, segmentation faults, or unexpected process restarts
• Establish baseline network traffic patterns and alert on deviations from the router's normal behavior

Monitoring Recommendations

• Enable comprehensive HTTP request logging on network perimeter devices monitoring traffic to Tenda F453 routers
• Configure SIEM alerts for repeated crash events or exploitation attempts against IoT devices
• Monitor for firmware integrity violations or unauthorized configuration changes on affected routers

How to Mitigate CVE-2026-3728

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Place affected Tenda F453 devices behind a firewall with strict ingress filtering
• Disable remote management features if not required for operations
• Monitor the Tenda Security Page for firmware updates addressing this vulnerability

Patch Information

As of the last modification date, no official patch information has been released by Tenda for this vulnerability. Organizations should monitor official vendor channels and the VulDB Report #349706 for updates on security patches. When a patch becomes available, apply it immediately following proper change management procedures.

Workarounds

• Implement network segmentation to isolate Tenda F453 routers from critical network assets
• Configure access control lists (ACLs) to restrict access to the /goform/setcfm endpoint
• Consider deploying a reverse proxy with input validation in front of the device management interface
• If feasible, replace vulnerable devices with supported alternatives that receive regular security updates

# Example: Block access to vulnerable endpoint using iptables
# Apply on a firewall protecting the Tenda F453 device
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -m string --string "/goform/setcfm" --algo bm -j DROP
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 443 -m string --string "/goform/setcfm" --algo bm -j DROP