CVE-2026-7033: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7033 Overview

A buffer overflow vulnerability has been discovered in Tenda F456 router firmware version 1.0.0.5. The vulnerability exists in the fromSafeClientFilter function located in the /goform/SafeClientFilter endpoint. Attackers can exploit this flaw by manipulating the menufacturer or Go arguments, leading to a buffer overflow condition that can be triggered remotely over the network.

Critical Impact
This buffer overflow vulnerability allows remote attackers to potentially execute arbitrary code or cause denial of service on affected Tenda F456 routers, compromising network security and device integrity.

Affected Products

Tenda F456 Firmware version 1.0.0.5
Tenda F456 Hardware

Discovery Timeline

2026-04-26 - CVE-2026-7033 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-7033

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The fromSafeClientFilter function in the Tenda F456 firmware fails to properly validate the length of user-supplied input through the menufacturer and Go parameters. When an attacker submits oversized input data to the /goform/SafeClientFilter endpoint, the function copies this data into a fixed-size buffer without adequate bounds checking, causing adjacent memory to be overwritten.

The network-accessible nature of this vulnerability makes it particularly dangerous for consumer and small business networks where Tenda F456 routers are deployed. The exploit has been publicly disclosed, increasing the risk of widespread exploitation attempts.

Root Cause

The root cause is improper bounds checking in the fromSafeClientFilter function when processing the menufacturer and Go parameters. The function allocates a fixed-size buffer for user input but does not validate that incoming data fits within the allocated space before copying it into memory. This classic buffer overflow pattern allows attackers to overwrite adjacent memory regions, potentially including return addresses or function pointers.

Attack Vector

The attack can be launched remotely over the network without requiring physical access to the device. An authenticated attacker with low privileges can send specially crafted HTTP requests to the /goform/SafeClientFilter endpoint with malicious payloads in the menufacturer or Go parameters. The buffer overflow can be triggered to corrupt memory, potentially leading to arbitrary code execution or device crashes.

The vulnerability can be exploited by crafting HTTP POST requests to the vulnerable endpoint with oversized parameter values. When the fromSafeClientFilter function processes these parameters without proper length validation, the buffer overflow occurs. Technical details and proof-of-concept information have been documented in the GitHub Vulnerability README and VulDB #359613.

Detection Methods for CVE-2026-7033

Indicators of Compromise

Unusual HTTP POST requests to /goform/SafeClientFilter with abnormally large parameter values
Router crashes, reboots, or unexpected behavior following web management interface access
Network traffic containing suspicious payloads targeting Tenda router endpoints
Log entries showing repeated access attempts to goform endpoints with malformed data

Detection Strategies

Monitor network traffic for HTTP requests to Tenda router management interfaces with oversized parameters
Deploy intrusion detection signatures targeting buffer overflow patterns in /goform/SafeClientFilter requests
Implement web application firewall rules to block requests exceeding expected parameter lengths
Review router access logs for anomalous patterns or repeated failed authentication attempts

Monitoring Recommendations

Enable logging on network perimeter devices to capture traffic destined for router management ports
Configure alerts for unusual traffic patterns to IoT and network infrastructure devices
Monitor for firmware integrity changes or unexpected device reboots
Implement network segmentation to isolate router management interfaces from untrusted networks

How to Mitigate CVE-2026-7033

Immediate Actions Required

Restrict access to the router's web management interface to trusted networks only
Disable remote management features if not required for operations
Implement network-level access controls to limit who can reach the router's administration interface
Monitor the Tenda Security Information page for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no official patch has been confirmed from Tenda for this vulnerability. Organizations should monitor official Tenda security channels and firmware release notes for updates. The vulnerability affects firmware version 1.0.0.5 of the Tenda F456 router. Additional technical details are available through VulDB Submission #798454.

Workarounds

Disable remote web management access and only allow local administration
Place the router behind a firewall that blocks external access to management ports
Use strong, unique credentials for router administration to limit authenticated attack surface
Consider network segmentation to isolate the vulnerable device from critical assets
Implement access control lists (ACLs) to restrict management interface access to specific IP addresses

bash

# Example network access restriction (varies by network equipment)
# Restrict access to router management 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