CVE-2026-3732: Tenda F453 Buffer Overflow Vulnerability

CVE-2026-3732 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda F453 firmware version 1.0.0.3. This security flaw exists in the strcpy function within the /goform/exeCommand file, where improper handling of the cmdinput argument allows an attacker to trigger a buffer overflow condition. The vulnerability can be exploited remotely, posing a significant threat to affected devices. The exploit details have been publicly disclosed, increasing the risk of exploitation in the wild.

Critical Impact

Remote attackers with low-level privileges can exploit this stack-based buffer overflow to potentially execute arbitrary code, compromise device integrity, and gain complete control over affected Tenda F453 routers.

Affected Products

• Tenda F453 Firmware version 1.0.0.3
• Tenda F453 Hardware devices

Discovery Timeline

• 2026-03-08 - CVE-2026-3732 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-3732

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 flaw resides in the web management interface of the Tenda F453 router, specifically within the /goform/exeCommand endpoint. When processing user-supplied input through the cmdinput parameter, the firmware uses the unsafe strcpy function without proper bounds checking.

The strcpy function copies data from a source buffer to a destination buffer without verifying that the destination has sufficient space to accommodate the input. When an attacker supplies an overly long string to the cmdinput parameter, the function writes beyond the allocated stack buffer, corrupting adjacent memory regions including return addresses and saved registers.

Since the attack vector is network-based and requires low privileges to execute, authenticated users with basic access can exploit this vulnerability. The impact is severe as successful exploitation can lead to complete compromise of confidentiality, integrity, and availability of the affected device.

Root Cause

The root cause of this vulnerability is the use of the unsafe strcpy function without implementing proper input validation or bounds checking on the cmdinput parameter. The firmware fails to verify the length of user-supplied input before copying it to a fixed-size stack buffer, creating a classic stack-based buffer overflow condition. This is a common coding error in embedded device firmware where memory-safe alternatives like strncpy or strlcpy should be used instead.

Attack Vector

The attack can be initiated remotely over the network through the device's web management interface. An attacker with low-level authentication can send a specially crafted HTTP request to the /goform/exeCommand endpoint containing a malicious cmdinput parameter value. The oversized input overflows the stack buffer, potentially allowing the attacker to:

1. Overwrite the return address on the stack
2. Redirect program execution to attacker-controlled shellcode
3. Execute arbitrary commands with the privileges of the web server process
4. Potentially gain full control of the router device

The vulnerability mechanism involves the unsafe use of strcpy to copy user-controlled data from the cmdinput parameter into a fixed-size stack buffer. When the input exceeds the buffer's capacity, memory corruption occurs, enabling potential code execution. For detailed technical analysis and proof-of-concept information, refer to the GitHub Vulnerability Report.

Detection Methods for CVE-2026-3732

Indicators of Compromise

• Unusual HTTP POST requests to /goform/exeCommand with abnormally long cmdinput parameter values
• Router crashes or unexpected reboots indicating potential exploitation attempts
• Anomalous outbound network connections from the router to unknown external IP addresses
• Modified router configuration settings or unauthorized administrative accounts

Detection Strategies

• Monitor HTTP traffic to the router's web interface for requests containing excessively long parameter values targeting /goform/exeCommand
• Implement intrusion detection rules to flag HTTP requests with cmdinput parameters exceeding normal expected lengths
• Deploy network segmentation to isolate IoT devices and enable better traffic monitoring
• Review router logs for repeated authentication attempts followed by requests to the vulnerable endpoint

Monitoring Recommendations

• Enable logging on the Tenda F453 device if available and forward logs to a centralized SIEM for analysis
• Configure network monitoring tools to alert on traffic patterns indicative of buffer overflow exploitation attempts
• Establish baseline behavior for normal router management traffic to identify anomalous activity
• Periodically audit device configuration for unauthorized changes

How to Mitigate CVE-2026-3732

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management if not required for operations
• Place the affected device behind a firewall with strict ingress rules blocking external access to the management interface
• Consider replacing the vulnerable device with a supported alternative if no patch is available

Patch Information

At the time of this publication, no vendor-issued patch has been confirmed for this vulnerability. Users should monitor the Tenda Official Website for firmware updates addressing CVE-2026-3732. Additional technical information is available through VulDB #349710.

Workarounds

• Implement network-level access controls to restrict management interface access to authorized administrators only
• Use a VPN to access the router's management interface rather than exposing it directly to the network
• Disable the web management interface entirely if command-line or alternative management methods are available
• Monitor for exploitation attempts using network intrusion detection systems with custom rules for this vulnerability

# Example: Restrict access to management interface using firewall rules
# Block external access to the router's web interface port
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP

# Allow only specific trusted admin IP
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT