CVE-2026-6122: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6122 Overview

A stack-based buffer overflow vulnerability has been discovered in the Tenda F451 router firmware version 1.0.0.7. The vulnerability exists in the frmL7ProtForm function within the /goform/L7Prot endpoint of the httpd component. An attacker can exploit this vulnerability by sending a maliciously crafted page argument to the affected endpoint, causing a buffer overflow on the stack that could lead to remote code execution or denial of service.

Critical Impact

This network-accessible vulnerability allows authenticated remote attackers to exploit a stack-based buffer overflow in the Tenda F451 router's web interface, potentially gaining full control of the affected device or causing service disruption.

Affected Products

• Tenda F451 firmware version 1.0.0.7
• Tenda F451 httpd component
• Devices running /goform/L7Prot endpoint

Discovery Timeline

• April 12, 2026 - CVE-2026-6122 published to NVD
• April 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6122

Vulnerability Analysis

This vulnerability is a classic stack-based buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) affecting the embedded web server (httpd) on the Tenda F451 router. The vulnerable function frmL7ProtForm handles HTTP requests to the /goform/L7Prot endpoint and processes the page parameter without proper bounds checking.

When an authenticated user submits a request to this endpoint, the page argument is copied to a stack buffer without validating the input length. An attacker can supply an oversized value that exceeds the allocated buffer, overwriting adjacent memory on the stack including the return address and potentially injecting shellcode for arbitrary code execution.

The vulnerability can be exploited remotely over the network, requiring only low-privilege authentication to access the affected goform endpoint. No user interaction is required once an attacker has network access to the device's management interface.

Root Cause

The root cause of this vulnerability is insufficient input validation in the frmL7ProtForm function. The function fails to verify the length of the page parameter before copying it to a fixed-size stack buffer. This allows attackers to write beyond the buffer boundary, corrupting the stack and potentially hijacking program execution flow.

The underlying issue is the use of unsafe memory copy operations without proper length constraints, a common vulnerability pattern in embedded device firmware that often relies on legacy C code without modern memory safety protections.

Attack Vector

The attack vector is network-based, targeting the HTTP daemon running on the Tenda F451 router. An attacker with low-privilege access to the router's web interface can send a specially crafted HTTP POST request to /goform/L7Prot with an oversized page parameter.

The exploitation workflow involves:

1. Gaining authenticated access to the router's web management interface
2. Crafting an HTTP request to /goform/L7Prot with a malicious page value
3. Overflowing the stack buffer to overwrite the return address
4. Redirecting execution to attacker-controlled code or achieving denial of service

The exploit has been publicly disclosed and may be used by threat actors targeting vulnerable devices. Technical details are available in the GitHub CVE Issue Discussion and VulDB Vulnerability #356985.

Detection Methods for CVE-2026-6122

Indicators of Compromise

• Unusual HTTP POST requests to /goform/L7Prot with abnormally long page parameters
• Crash logs or unexpected restarts of the httpd service on Tenda F451 devices
• Anomalous outbound connections from router devices following web interface access
• Evidence of shell access or command execution originating from the router

Detection Strategies

• Monitor network traffic for HTTP requests to /goform/L7Prot containing page parameters exceeding expected lengths
• Implement intrusion detection rules to flag oversized POST payloads targeting Tenda router goform endpoints
• Review router access logs for repeated or suspicious requests to the L7Prot endpoint
• Deploy network segmentation to isolate IoT and router management interfaces from untrusted networks

Monitoring Recommendations

• Enable verbose logging on network perimeter devices to capture HTTP traffic to router management interfaces
• Implement alerting for httpd process crashes or unexpected service restarts on Tenda devices
• Conduct regular firmware version audits to identify devices running vulnerable version 1.0.0.7
• Monitor for connections to known malicious infrastructure from network devices

How to Mitigate CVE-2026-6122

Immediate Actions Required

• Restrict access to the Tenda F451 web management interface to trusted IP addresses only
• Disable remote management features if not required for operations
• Implement network segmentation to isolate router management interfaces from the internet
• Monitor for vendor firmware updates from Tenda and apply patches when available

Patch Information

At the time of publication, no official patch has been confirmed by Tenda. Organizations should monitor the Tenda official website for security advisories and firmware updates. Consider replacing affected devices if patches are not released in a timely manner.

Additional vulnerability details and community discussions are available via the VulDB Submission #792872 and threat intelligence at VulDB CTI for #356985.

Workarounds

• Configure firewall rules to block external access to the router's HTTP management port (typically port 80 or 443)
• Use VPN or other secure access methods instead of exposing the management interface directly
• Implement strong authentication credentials and limit administrative accounts
• Consider deploying a network-based web application firewall to filter malicious requests to the goform endpoints

# Example iptables rule to restrict management interface access
# Allow only trusted management network (192.168.1.0/24)
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP