CVE-2026-6198: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-6198 Overview

A stack-based buffer overflow vulnerability has been discovered in Tenda F456 router firmware version 1.0.0.5. This vulnerability affects the fromNatStaticSetting function located in the /goform/NatStaticSetting file. An attacker can exploit this vulnerability by manipulating the page argument to trigger a stack-based buffer overflow condition. The vulnerability is remotely exploitable and has been publicly disclosed.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code, crash the device, or gain unauthorized control over the affected Tenda F456 router without physical access.

Affected Products

• Tenda F456 firmware version 1.0.0.5

Discovery Timeline

• April 13, 2026 - CVE-2026-6198 published to NVD
• April 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6198

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromNatStaticSetting function in the Tenda F456 router firmware fails to properly validate the length of the page argument before copying it to a stack buffer. When an attacker supplies an overly long string for the page parameter, the buffer overflow can overwrite adjacent stack memory, including saved return addresses and other critical data structures.

The network-accessible nature of this vulnerability makes it particularly concerning for home and small office environments where Tenda routers are commonly deployed. An authenticated attacker with low privileges can remotely trigger this overflow through the web management interface, potentially leading to full device compromise.

Root Cause

The root cause of CVE-2026-6198 is insufficient input validation in the fromNatStaticSetting function. The function accepts user-controlled input through the page parameter via the /goform/NatStaticSetting endpoint but does not perform adequate bounds checking before copying the data to a fixed-size stack buffer. This allows attackers to supply input exceeding the buffer's allocated size, resulting in stack memory corruption.

Attack Vector

The attack vector for this vulnerability is network-based, requiring the attacker to have authenticated access to the router's web management interface. The exploitation flow involves:

1. An attacker authenticates to the Tenda F456 web interface with low-privilege credentials
2. The attacker crafts a malicious HTTP request to /goform/NatStaticSetting
3. The page parameter is populated with an oversized payload designed to overflow the stack buffer
4. The fromNatStaticSetting function processes the request and copies the malicious input without proper bounds checking
5. The stack overflow corrupts adjacent memory, potentially allowing code execution or denial of service

The vulnerability requires no user interaction once an attacker has authenticated access, making it suitable for automated exploitation in targeted attacks against network infrastructure.

Detection Methods for CVE-2026-6198

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/NatStaticSetting with abnormally long page parameter values
• Router crashes or unexpected reboots following web interface access
• Anomalous network traffic originating from the Tenda F456 device to unknown external hosts
• Modified router configuration or firmware settings without administrator action

Detection Strategies

• Monitor web server logs for HTTP requests to /goform/NatStaticSetting containing unusually long parameter strings
• Implement network intrusion detection rules to identify buffer overflow payloads in HTTP traffic destined for Tenda router management interfaces
• Deploy anomaly detection to identify unusual patterns in router behavior such as unexpected restarts or configuration changes
• Use SentinelOne Singularity to monitor for exploitation attempts and post-compromise activity on network devices

Monitoring Recommendations

• Enable verbose logging on network firewalls and intrusion detection systems for traffic to router management interfaces
• Establish baseline behavior for router management interface access and alert on deviations
• Regularly audit router configurations and firmware versions to ensure they remain unmodified
• Implement network segmentation to isolate router management interfaces from untrusted network segments

How to Mitigate CVE-2026-6198

Immediate Actions Required

• Restrict access to the Tenda F456 web management interface to trusted IP addresses only
• Disable remote management functionality if not required for operations
• Place the router management interface behind a VPN or dedicated management network
• Monitor for firmware updates from Tenda that address this vulnerability
• Consider replacing affected devices with alternative products if no patch is forthcoming

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for security updates and firmware releases. Additional technical details are available through the GitHub Vulnerability Documentation and VulDB Vulnerability Entry.

Workarounds

• Implement firewall rules to restrict access to the /goform/NatStaticSetting endpoint from untrusted networks
• Use access control lists (ACLs) on upstream network devices to limit management interface exposure
• Deploy a web application firewall (WAF) in front of the router management interface to filter malicious requests
• Consider network segmentation to isolate the router from direct internet access

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