CVE-2026-3380: Tenda F453 Firmware Buffer Overflow Flaw

CVE-2026-3380 Overview

A buffer overflow vulnerability has been identified in Tenda F453 firmware version 1.0.0.3. This security flaw exists within the frmL7ImForm function located in the /goform/L7Im file. The vulnerability is triggered through improper handling of the page argument, which can be exploited by remote attackers to cause a buffer overflow condition. The exploit has been publicly disclosed, increasing the risk of active exploitation attempts targeting vulnerable devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code, crash the device, or gain unauthorized access to the affected Tenda F453 router, compromising network security and integrity.

Affected Products

• Tenda F453 Firmware version 1.0.0.3
• Tenda F453 Hardware Device

Discovery Timeline

• March 1, 2026 - CVE-2026-3380 published to NVD
• March 3, 2026 - Last updated in NVD database

Technical Details for CVE-2026-3380

Vulnerability Analysis

This buffer overflow vulnerability (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) affects the web management interface of the Tenda F453 router. The vulnerable function frmL7ImForm fails to properly validate the length of user-supplied input passed through the page parameter before copying it into a fixed-size memory buffer. When an attacker sends a specially crafted HTTP request with an oversized page argument to the /goform/L7Im endpoint, the function writes beyond the allocated buffer boundaries, corrupting adjacent memory regions.

This memory corruption can lead to denial of service through device crashes, and in more sophisticated attack scenarios, could potentially allow remote code execution if an attacker can precisely control the overflow to overwrite return addresses or function pointers. The network-accessible nature of the web interface combined with the low complexity of exploitation makes this vulnerability particularly concerning for exposed devices.

Root Cause

The root cause of this vulnerability is insufficient bounds checking in the frmL7ImForm function when processing the page parameter. The firmware code copies user-controlled input directly into a stack or heap buffer without validating that the input length does not exceed the destination buffer's capacity. This classic buffer overflow pattern results from inadequate input validation and memory safety controls within the embedded firmware's web request handling code.

Attack Vector

The vulnerability is exploitable remotely over the network through the router's web management interface. An authenticated attacker (low privilege required) can send a malicious HTTP request to the /goform/L7Im endpoint with a crafted page parameter containing excessive data. The attack does not require user interaction and can be automated, making it suitable for inclusion in router exploitation frameworks.

The exploitation flow involves:

1. Identifying a vulnerable Tenda F453 device running firmware 1.0.0.3
2. Authenticating to the web management interface
3. Sending a POST request to /goform/L7Im with an oversized page parameter
4. Triggering the buffer overflow in frmL7ImForm function
5. Achieving denial of service or potential code execution

Technical details and proof-of-concept information are available in the GitHub Vulnerability Repository.

Detection Methods for CVE-2026-3380

Indicators of Compromise

• Unexpected device reboots or crashes of Tenda F453 routers
• Anomalous HTTP POST requests to /goform/L7Im with unusually large page parameter values
• Web server logs showing repeated requests to the L7Im endpoint with malformed data
• Memory corruption signatures or crash dumps from affected devices

Detection Strategies

• Monitor network traffic for HTTP POST requests to /goform/L7Im containing abnormally large parameter values
• Implement intrusion detection rules to flag requests with page parameter exceeding expected length thresholds
• Deploy web application firewall rules to validate input lengths on router management interfaces
• Review device logs for unexpected service restarts or firmware crashes

Monitoring Recommendations

• Enable logging on network perimeter devices to capture traffic destined for router management interfaces
• Configure SIEM alerts for repeated authentication attempts followed by requests to /goform/L7Im
• Monitor for unusual outbound traffic patterns from router devices that may indicate compromise
• Implement network segmentation to isolate management interfaces from untrusted networks

How to Mitigate CVE-2026-3380

Immediate Actions Required

• Restrict access to the Tenda F453 web management interface to trusted IP addresses only
• Disable remote web administration if not required for operations
• Implement firewall rules to block external access to the router's management port
• Monitor for firmware updates from Tenda that address this vulnerability
• Consider network segmentation to isolate vulnerable devices

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Administrators should monitor the Tenda Website for firmware updates addressing this security issue. Additional technical details are available through VulDB #348265.

Workarounds

• Configure access control lists (ACLs) to limit web management access to specific trusted IP addresses
• Place the router management interface on a dedicated management VLAN inaccessible from general network segments
• Use a VPN to access router management rather than exposing the interface directly
• Implement upstream network filtering to block malicious requests before they reach the device

# Example: Restrict management access via iptables on upstream firewall
# Block external access to router management interface
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 subnet
iptables -I FORWARD -s 192.168.100.0/24 -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT