CVE-2026-7031: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7031 Overview

A buffer overflow vulnerability has been identified in Tenda F456 router firmware version 1.0.0.5. This vulnerability exists in the fromSafeMacFilter function located in the /goform/SafeMacFilter endpoint. By manipulating the page argument, an attacker can trigger a buffer overflow condition. The vulnerability is remotely exploitable, and a public exploit is available, significantly increasing the risk to affected devices.

Critical Impact
Remote attackers with low privileges can exploit this buffer overflow to potentially execute arbitrary code, crash the device, or gain unauthorized control over the router, compromising network security.

Affected Products

Tenda F456 Firmware version 1.0.0.5
Tenda F456 Hardware

Discovery Timeline

2026-04-26 - CVE-2026-7031 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-7031

Vulnerability Analysis

This vulnerability is classified as a buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the web management interface of the Tenda F456 router, specifically within the fromSafeMacFilter function that handles MAC address filtering functionality.

When processing HTTP requests to the /goform/SafeMacFilter endpoint, the function fails to properly validate the length of the page parameter before copying it into a fixed-size buffer. This allows an attacker to supply a crafted input that exceeds the buffer boundaries, potentially overwriting adjacent memory and corrupting program execution flow.

The network-accessible nature of this vulnerability combined with the low attack complexity makes it particularly dangerous for devices exposed on local networks or, in misconfigured scenarios, the internet.

Root Cause

The root cause of this vulnerability is improper input validation in the fromSafeMacFilter function. The code does not perform adequate bounds checking on the page argument before processing, allowing attackers to supply oversized input that overflows the allocated buffer space. This is a classic memory safety issue common in C/C++ codebases where manual memory management is required.

Attack Vector

The attack can be launched remotely over the network by sending a specially crafted HTTP POST request to the /goform/SafeMacFilter endpoint. The attacker needs low-level authentication to access the vulnerable endpoint. By manipulating the page parameter with an excessively long value, the attacker can overflow the buffer and potentially:

Crash the router causing denial of service
Overwrite return addresses to redirect code execution
Execute arbitrary code with the privileges of the web server process

The vulnerability has been publicly disclosed with proof-of-concept code available in the GitHub PoC Repository, which attackers could leverage to develop working exploits.

Detection Methods for CVE-2026-7031

Indicators of Compromise

Abnormally long HTTP POST requests to /goform/SafeMacFilter endpoint
Unexpected router crashes or reboots
Unusual outbound connections from the router to unknown IP addresses
Modified router configuration or firewall rules without administrator action
Presence of unauthorized user accounts or SSH keys on the device

Detection Strategies

Monitor HTTP traffic to router management interfaces for requests containing oversized page parameters
Implement network intrusion detection rules to flag malformed requests to /goform/SafeMacFilter
Deploy web application firewall rules to block requests with abnormally long parameter values
Review router access logs for repeated failed authentication attempts followed by successful exploitation patterns

Monitoring Recommendations

Enable and regularly review router access logs for suspicious activity
Configure network monitoring to alert on unexpected traffic patterns to/from router management ports
Implement baseline monitoring for router CPU and memory usage to detect exploitation attempts
Set up automated alerts for router configuration changes or unexpected reboots

How to Mitigate CVE-2026-7031

Immediate Actions Required

Restrict access to the router management interface to trusted IP addresses only
Disable remote management if not required for operations
Segment the network to isolate the vulnerable router from critical systems
Monitor the Tenda Official Website for firmware updates addressing this vulnerability
Consider replacing affected devices if no patch becomes available

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor vendor communications and security advisories for updates. Additional technical details are available through the VulDB Entry.

Workarounds

Restrict management interface access to specific trusted IP addresses using firewall rules
Disable the web management interface if possible and use alternative management methods
Place the router behind a firewall that can filter malicious requests to the /goform/SafeMacFilter endpoint
Implement network segmentation to limit the impact of a potential compromise
Consider deploying a replacement router from a different vendor until a patch is available

bash

# Example: Restrict router management access using iptables on upstream firewall
# Block external access to router management port (adjust IP and port as needed)
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow only trusted management workstation
iptables -I FORWARD -s 192.168.1.100 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT