CVE-2026-6124: Tenda F451 Buffer Overflow Vulnerability

CVE-2026-6124 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda F451 router firmware version 1.0.0.7. This vulnerability affects the fromSafeMacFilter function within the /goform/SafeMacFilter endpoint of the router's embedded httpd web server. Remote attackers can exploit this flaw by manipulating the page or menufacturer arguments, potentially leading to arbitrary code execution or denial of service on affected devices.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code or crash the device, compromising network security and availability.

Affected Products

• Tenda F451 Firmware version 1.0.0.7
• Tenda F451 httpd web server component
• Devices running vulnerable /goform/SafeMacFilter endpoint

Discovery Timeline

• 2026-04-12 - CVE-2026-6124 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2026-6124

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists in the fromSafeMacFilter function which handles MAC address filtering configuration through the router's web interface. When processing user-supplied input via the page or menufacturer parameters, the function fails to properly validate the length of the input data before copying it to a fixed-size stack buffer.

The vulnerability allows remote authenticated attackers to send specially crafted HTTP requests to the /goform/SafeMacFilter endpoint. Due to insufficient bounds checking, oversized input values can overflow the stack buffer, potentially overwriting adjacent memory including saved return addresses and function pointers.

Root Cause

The root cause of this vulnerability is improper input validation in the fromSafeMacFilter function. The function uses unsafe string handling operations that do not verify the length of user-supplied data before copying it into a stack-allocated buffer. This classic buffer overflow pattern allows attackers to write beyond the intended buffer boundaries.

Attack Vector

The attack can be executed remotely over the network by sending malicious HTTP POST requests to the vulnerable /goform/SafeMacFilter endpoint. The attacker must be authenticated (low privilege requirement) but no user interaction is required. By supplying an excessively long value in the page or menufacturer parameter, an attacker can trigger the stack-based buffer overflow.

The exploitation mechanism involves sending a crafted HTTP request with oversized parameter values that exceed the expected buffer size. When the vulnerable function processes these parameters without proper length validation, the overflow occurs, potentially allowing the attacker to overwrite critical stack data. For detailed technical analysis, refer to the GitHub Issue documenting this vulnerability.

Detection Methods for CVE-2026-6124

Indicators of Compromise

• Unusual HTTP POST requests to /goform/SafeMacFilter with abnormally long parameter values
• Router crashes or unexpected reboots following web interface access
• Anomalous network traffic patterns originating from or directed at the router's management interface
• System logs showing repeated access attempts to the SafeMacFilter endpoint

Detection Strategies

• Monitor HTTP traffic for requests to /goform/SafeMacFilter containing oversized page or menufacturer parameters
• Implement network intrusion detection rules to flag HTTP requests with parameter values exceeding normal length thresholds
• Review router logs for authentication attempts followed by configuration endpoint access
• Deploy web application firewall rules to inspect and block malformed requests to Tenda router endpoints

Monitoring Recommendations

• Enable logging on network perimeter devices for traffic destined to router management interfaces
• Configure alerts for multiple failed or suspicious requests to Tenda device endpoints
• Implement network segmentation to restrict access to router management interfaces from untrusted networks
• Regularly audit access logs for the httpd web server component

How to Mitigate CVE-2026-6124

Immediate Actions Required

• Restrict network access to the router's web management interface to trusted IP addresses only
• Disable remote management access if not required for operations
• Implement firewall rules to block external access to port 80/443 on affected Tenda devices
• Monitor for firmware updates from Tenda that address this vulnerability

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. Additional vulnerability details are available through VulDB #356987 and the associated CTI Report.

Workarounds

• Implement network segmentation to isolate affected devices from untrusted network segments
• Use access control lists (ACLs) to limit which hosts can reach the router's management interface
• Consider deploying a reverse proxy with input validation in front of the device if remote management is required
• Replace affected devices with alternatives if patches are not forthcoming

# Example: Restrict management interface access via iptables on upstream firewall
iptables -A FORWARD -d <TENDA_ROUTER_IP> -p tcp --dport 80 -s <TRUSTED_MGMT_SUBNET> -j ACCEPT
iptables -A FORWARD -d <TENDA_ROUTER_IP> -p tcp --dport 80 -j DROP