CVE-2026-7082: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7082 Overview

A buffer overflow vulnerability has been discovered in Tenda F456 firmware version 1.0.0.5. The vulnerability affects the formWrlExtraSet function within the /goform/WrlExtraSet endpoint of the httpd component. When the Go argument is manipulated with malicious input, the application fails to properly validate buffer boundaries, resulting in a classic buffer overflow condition. This flaw can be exploited remotely by authenticated attackers to potentially execute arbitrary code or cause denial of service on the affected device.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to compromise the confidentiality, integrity, and availability of affected Tenda F456 routers, potentially gaining full control of the network device.

Affected Products

• Tenda F456 Firmware version 1.0.0.5
• Tenda F456 Hardware Device

Discovery Timeline

• 2026-04-27 - CVE-2026-7082 published to NVD
• 2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7082

Vulnerability Analysis

This vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The affected function formWrlExtraSet in the httpd web service component does not adequately validate the length of user-supplied input passed through the Go argument before copying it into a fixed-size memory buffer.

When processing HTTP requests to /goform/WrlExtraSet, the router's web management interface accepts the Go parameter without proper bounds checking. This allows an attacker to supply an oversized input value that overflows the allocated buffer space, potentially overwriting adjacent memory regions including return addresses, function pointers, or other critical data structures.

The vulnerability is network-accessible, meaning attackers can target the device remotely through its web management interface. While authentication is required to access the vulnerable endpoint, this still presents a significant risk in scenarios where default credentials are in use or where an attacker has obtained valid authentication credentials.

Root Cause

The root cause of this vulnerability lies in the improper handling of user-controlled input within the formWrlExtraSet function. The function fails to implement adequate bounds checking when processing the Go argument, allowing data to be written beyond the boundaries of the allocated buffer. This is a classic example of unsafe memory operations in embedded firmware where input validation is often insufficient due to resource constraints or legacy code practices.

Attack Vector

The attack vector is network-based, targeting the httpd web service running on the Tenda F456 router. An authenticated attacker can craft a malicious HTTP request to the /goform/WrlExtraSet endpoint with an oversized Go parameter value. When the vulnerable function processes this input, the buffer overflow condition is triggered.

The exploitation process involves sending a specially crafted HTTP POST request containing the malicious payload in the Go parameter. Upon successful exploitation, an attacker could achieve code execution within the context of the httpd service, which typically runs with elevated privileges on embedded devices.

Technical details and proof-of-concept information have been documented in the GitHub README for VulDB Report. Additional vulnerability details are available through VulDB Vulnerability #359657.

Detection Methods for CVE-2026-7082

Indicators of Compromise

• Unusual HTTP POST requests to /goform/WrlExtraSet with abnormally large Go parameter values
• Unexpected crashes or restarts of the httpd service on Tenda F456 devices
• Anomalous network traffic patterns targeting the router's web management interface
• Signs of unauthorized configuration changes or access to the device

Detection Strategies

• Monitor HTTP traffic to Tenda F456 devices for requests containing oversized parameters in POST data to /goform/WrlExtraSet
• Implement intrusion detection rules to flag buffer overflow attack patterns targeting the identified endpoint
• Review device logs for httpd service crashes or abnormal termination events
• Deploy network monitoring to detect unusual traffic volumes or patterns directed at router management interfaces

Monitoring Recommendations

• Enable logging on network firewalls and IDS/IPS systems to capture traffic destined for router management ports
• Implement alerting for repeated failed authentication attempts followed by successful access to the vulnerable endpoint
• Monitor for firmware integrity changes that could indicate post-exploitation persistence
• Track device behavior anomalies such as unexpected reboots or configuration modifications

How to Mitigate CVE-2026-7082

Immediate Actions Required

• Restrict access to the router's web management interface to trusted networks or IP addresses only
• Change default credentials immediately if still in use and implement strong authentication
• Disable remote management if not required for operations
• Place the router behind a firewall that blocks external access to management interfaces
• Monitor the Tenda Security Information page for firmware updates addressing this vulnerability

Patch Information

At the time of publication, no official patch has been released by Tenda to address this vulnerability. Organizations using affected Tenda F456 devices with firmware version 1.0.0.5 should implement the recommended workarounds and monitor vendor communications for security updates.

For the latest vulnerability information, refer to VulDB Submission #798465 and the VulDB CTI for #359657.

Workarounds

• Implement network segmentation to isolate affected devices from untrusted networks
• Configure firewall rules to restrict access to the httpd management interface (typically port 80 or 443)
• Use a VPN for any required remote administration rather than exposing the management interface directly
• Consider replacing affected devices with alternatives that have active security support if patches are not forthcoming

# Example: Firewall rule to restrict access to router management interface
# Block external access to the router's web interface
iptables -A INPUT -p tcp --dport 80 -s ! 192.168.1.0/24 -j DROP
iptables -A INPUT -p tcp --dport 443 -s ! 192.168.1.0/24 -j DROP