CVE-2026-7101: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-7101 Overview

A buffer overflow vulnerability has been discovered in Tenda F456 router firmware version 1.0.0.5. The vulnerability exists within the fromWrlclientSet function located in the /goform/WrlclientSet endpoint of the httpd component. Improper memory bounds checking during input manipulation allows remote attackers to trigger a buffer overflow condition, potentially leading to arbitrary code execution or denial of service.

Critical Impact
This network-accessible vulnerability in Tenda F456 routers allows authenticated remote attackers to exploit a buffer overflow condition in the httpd service, potentially compromising the entire device and any connected network infrastructure.

Affected Products

Tenda F456 Firmware version 1.0.0.5
Tenda F456 Hardware devices running vulnerable firmware

Discovery Timeline

2026-04-27 - CVE-2026-7101 published to NVD
2026-04-29 - Last updated in NVD database

Technical Details for CVE-2026-7101

Vulnerability Analysis

This buffer overflow vulnerability (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer) affects the web management interface of Tenda F456 routers. The vulnerable function fromWrlclientSet fails to properly validate the size of user-supplied input before copying it into a fixed-size memory buffer. When processing requests to the /goform/WrlclientSet endpoint, the httpd daemon does not perform adequate boundary checks, allowing an attacker to write data beyond the allocated buffer space.

The exploit has been disclosed publicly, increasing the urgency for remediation. While the attack requires low privileges to execute, no user interaction is needed once the attacker has network access to the device's management interface.

Root Cause

The root cause of this vulnerability lies in the fromWrlclientSet function's failure to implement proper bounds checking when handling user-controlled input. The httpd component processes HTTP requests to the /goform/WrlclientSet endpoint without validating input length, allowing data to overflow beyond the intended memory boundaries. This is a classic example of unsafe memory operations in embedded device firmware where input sanitization is insufficient or absent entirely.

Attack Vector

The attack vector for CVE-2026-7101 is network-based, meaning an attacker with network access to the router's management interface can exploit this vulnerability remotely. The attacker must have low-level privileges (authenticated access) to the device. The attack requires no user interaction and has low complexity to execute.

An attacker would craft a malicious HTTP request to the /goform/WrlclientSet endpoint containing an oversized payload designed to overflow the target buffer. Successful exploitation could allow the attacker to overwrite adjacent memory regions, potentially hijacking program execution flow, crashing the httpd service, or executing arbitrary code with the privileges of the web server process.

Technical details and proof-of-concept information are available in the GitHub PoC Repository.

Detection Methods for CVE-2026-7101

Indicators of Compromise

Unusual HTTP POST requests to /goform/WrlclientSet containing abnormally large payloads
Unexpected crashes or restarts of the httpd service on Tenda F456 devices
Anomalous network traffic patterns targeting the router's management interface
Authentication logs showing repeated access attempts to the web management portal

Detection Strategies

Monitor network traffic for HTTP requests to /goform/WrlclientSet endpoints with payload sizes exceeding normal operational parameters
Implement intrusion detection rules to flag oversized POST requests targeting Tenda router management interfaces
Deploy network segmentation to isolate router management interfaces from untrusted network segments
Review system logs for httpd service crashes or unexpected behavior patterns

Monitoring Recommendations

Enable comprehensive logging on network perimeter devices to capture traffic to internal router management interfaces
Configure SIEM rules to alert on potential buffer overflow exploitation patterns targeting embedded devices
Regularly audit firmware versions across all Tenda F456 devices to identify vulnerable instances
Monitor for reconnaissance activity targeting router management ports (typically HTTP/HTTPS)

How to Mitigate CVE-2026-7101

Immediate Actions Required

Restrict network access to the Tenda F456 management interface to trusted administrator IP addresses only
Disable remote management access from WAN interfaces if not explicitly required
Implement network segmentation to isolate router management interfaces from general network traffic
Monitor for exploitation attempts using network intrusion detection systems

Patch Information

As of the last update on 2026-04-29, users should check the Tenda Official Website for firmware updates addressing this vulnerability. Review the VulDB Vulnerability Details for the latest remediation guidance and patch availability status.

Workarounds

Configure firewall rules to restrict access to the /goform/WrlclientSet endpoint from untrusted sources
Implement network access control lists (ACLs) limiting management interface access to specific administrator workstations
Consider placing vulnerable devices behind a reverse proxy that can filter malicious requests
Disable the httpd service entirely if web-based management is not required for operations

bash

# Example: Restrict management interface access using firewall rules
# Block external access to router management ports
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

# Allow only specific admin IP to access management interface
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.100 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP