CVE-2026-6120: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6120 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda F451 router firmware version 1.0.0.7. The vulnerability exists in the fromDhcpListClient function within the /goform/DhcpListClient endpoint of the httpd component. When the page argument is manipulated, improper bounds checking allows an attacker to trigger a stack-based buffer overflow. This vulnerability can be exploited remotely over the network, and a public exploit is reportedly available.

Critical Impact

Remote attackers can exploit this stack-based buffer overflow to potentially achieve code execution on affected Tenda F451 routers, compromising network infrastructure security.

Affected Products

• Tenda F451 Firmware version 1.0.0.7
• Tenda F451 httpd component (/goform/DhcpListClient endpoint)

Discovery Timeline

• 2026-04-12 - CVE-2026-6120 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2026-6120

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromDhcpListClient function in the Tenda F451's httpd service fails to properly validate the length of the page parameter before copying it to a fixed-size stack buffer. When an attacker supplies an overly long value for this parameter, the data overflows the allocated buffer on the stack, potentially overwriting adjacent memory including the function's return address.

The network-accessible nature of this vulnerability means that any attacker who can reach the router's web management interface can attempt exploitation. The httpd component processes HTTP requests to the /goform/DhcpListClient endpoint without requiring authentication for the vulnerable code path.

Root Cause

The root cause is improper input validation in the fromDhcpListClient function. The code does not enforce adequate length checks on the page argument before processing it, allowing user-controlled data to overflow stack memory boundaries. This is a classic case of unsafe string handling in embedded device firmware, where memory-constrained environments often lack comprehensive input sanitization.

Attack Vector

The attack can be launched remotely over the network by sending a crafted HTTP request to the vulnerable endpoint. An attacker would target the /goform/DhcpListClient endpoint and supply a malicious page parameter containing an excessively long payload designed to overflow the stack buffer. Upon successful exploitation, the attacker may be able to control the execution flow of the httpd process, potentially leading to arbitrary code execution with the privileges of the web server process.

The vulnerability is exploitable without user interaction, and given that the exploit is publicly available, organizations with exposed Tenda F451 devices face heightened risk. For additional technical details, refer to the GitHub Issue Tracker and the VulDB vulnerability entry.

Detection Methods for CVE-2026-6120

Indicators of Compromise

• Unexpected HTTP requests to /goform/DhcpListClient with abnormally long page parameter values
• Httpd service crashes or restarts on Tenda F451 devices
• Unusual network traffic patterns targeting the router's web management interface
• System log entries indicating buffer overflow or memory corruption errors

Detection Strategies

• Monitor and log all HTTP requests to the /goform/DhcpListClient endpoint for anomalous parameter lengths
• Implement network-based intrusion detection rules to identify buffer overflow exploit patterns targeting Tenda routers
• Deploy endpoint protection solutions capable of detecting exploitation attempts against embedded devices
• Use SentinelOne Singularity to monitor network segments containing IoT and router devices for suspicious activity

Monitoring Recommendations

• Enable verbose logging on network firewalls to capture traffic destined for router management interfaces
• Regularly review httpd logs on Tenda F451 devices for evidence of exploitation attempts
• Implement network segmentation to isolate router management interfaces from untrusted networks
• Consider deploying honeypot devices to detect reconnaissance and exploitation attempts

How to Mitigate CVE-2026-6120

Immediate Actions Required

• Restrict access to the Tenda F451 web management interface to trusted IP addresses only
• Disable remote management access if not required for operations
• Place Tenda F451 devices behind a firewall that blocks external access to the management interface
• Monitor for firmware updates from Tenda and apply them as soon as available

Patch Information

At the time of publication, no official patch from Tenda has been confirmed for this vulnerability. Organizations should monitor the Tenda Official Website for firmware updates addressing this issue. Until a patch is available, implementing network-based mitigations is strongly recommended.

Workarounds

• Configure firewall rules to block external access to /goform/DhcpListClient and related management endpoints
• Implement access control lists (ACLs) to restrict management interface access to specific administrator IP addresses
• Consider replacing affected devices with alternatives that have better security support if no patch becomes available
• Use a VPN for remote administration rather than exposing the management interface directly to the internet

# Example iptables rule to restrict access to the management interface
# Replace 192.168.1.100 with your admin IP and eth0 with your WAN interface
iptables -A INPUT -i eth0 -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP