CVE-2026-7079: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7079 Overview

A buffer overflow vulnerability has been identified in the Tenda F456 router firmware version 1.0.0.5. This security flaw affects the fromAdvSetWan function within the /goform/AdvSetWan endpoint of the httpd component. An attacker can remotely exploit this vulnerability by manipulating the wanmode argument, leading to a buffer overflow condition that could result in arbitrary code execution or denial of service on the affected device.

Critical Impact

This network-accessible buffer overflow vulnerability allows authenticated remote attackers to compromise the router's integrity, potentially gaining full control over the device and enabling lateral movement within the network.

Affected Products

• Tenda F456 Firmware version 1.0.0.5
• Tenda F456 Hardware

Discovery Timeline

• 2026-04-27 - CVE-2026-7079 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7079

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromAdvSetWan function in the Tenda F456 router's httpd web service fails to properly validate the length of user-supplied input in the wanmode parameter before copying it to a fixed-size buffer. When an attacker provides an oversized value for this parameter, the data overflows the allocated buffer, potentially overwriting adjacent memory regions including return addresses or function pointers.

The httpd component serves as the primary web management interface for the router, making this vulnerability particularly concerning as it handles network configuration requests. The buffer overflow occurs in the context of the web server process, which typically runs with elevated privileges on embedded devices.

Root Cause

The root cause of this vulnerability is improper bounds checking in the fromAdvSetWan function when processing the wanmode argument. The function accepts user-controlled input from HTTP POST requests to /goform/AdvSetWan and copies this data into a stack or heap buffer without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow pattern is common in embedded device firmware where memory safety practices may be less rigorous than in mainstream software development.

Attack Vector

The vulnerability is exploitable over the network via the router's web management interface. An attacker with low-privilege access to the router's administrative interface can craft a malicious HTTP POST request to the /goform/AdvSetWan endpoint containing an oversized wanmode parameter value.

The attack does not require user interaction and can be performed remotely. Successful exploitation could allow an attacker to execute arbitrary code on the router, modify device configurations, intercept network traffic, or use the compromised device as a pivot point for further network intrusion.

Technical details and proof-of-concept information have been documented in the GitHub Repository README and additional context is available through VulDB #359654.

Detection Methods for CVE-2026-7079

Indicators of Compromise

• Unusual HTTP POST requests to /goform/AdvSetWan with abnormally large wanmode parameter values
• Unexpected router reboots or crashes indicative of memory corruption
• Modified router configurations that were not authorized by administrators
• Anomalous outbound connections from the router to unknown external IP addresses

Detection Strategies

• Implement network intrusion detection rules to monitor for HTTP requests to /goform/AdvSetWan with payload sizes exceeding normal operational parameters
• Deploy web application firewall rules to inspect and block requests containing oversized parameter values targeting Tenda router endpoints
• Enable logging on the router (if available) and monitor for repeated access attempts to the affected endpoint
• Use network traffic analysis to identify patterns consistent with exploitation attempts

Monitoring Recommendations

• Continuously monitor network traffic for suspicious activity targeting router management interfaces
• Establish baseline metrics for normal router behavior and alert on deviations such as unexpected restarts or configuration changes
• Implement network segmentation to restrict access to router management interfaces from untrusted network segments

How to Mitigate CVE-2026-7079

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only using firewall rules
• Disable remote management access if not operationally required
• Segment the network to isolate the router's management interface from untrusted networks
• Monitor for firmware updates from Tenda and apply patches as soon as they become available

Patch Information

At the time of this publication, no official patch has been released by Tenda for this vulnerability. Administrators should monitor the Tenda Official Website for security advisories and firmware updates addressing CVE-2026-7079. Given the public availability of exploitation information, organizations should prioritize implementing workarounds until an official fix is released.

Workarounds

• Configure access control lists (ACLs) to restrict access to the /goform/AdvSetWan endpoint
• Place the router behind a network firewall that can filter malicious requests
• Consider temporarily disabling the web management interface and using alternative management methods if available
• Implement network-based intrusion prevention systems to block exploitation attempts

# Example iptables rule to restrict access to router management interface
# Apply on upstream firewall or management network
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP