CVE-2026-6197: Tenda F456 Buffer Overflow Vulnerability

CVE-2026-6197 Overview

A stack-based buffer overflow vulnerability has been identified in the Tenda F456 router firmware version 1.0.0.5. This vulnerability exists in the formWrlsafeset function located in the /goform/AdvSetWrlsafeset file. By manipulating the mit_ssid argument, an attacker can trigger a stack-based buffer overflow condition. The vulnerability is remotely exploitable, and proof-of-concept exploit code has been published publicly.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability to potentially execute arbitrary code or cause denial of service on affected Tenda F456 routers. The network-accessible nature of the vulnerability significantly increases the risk of exploitation.

Affected Products

• Tenda F456 Firmware Version 1.0.0.5

Discovery Timeline

• April 13, 2026 - CVE-2026-6197 published to NVD
• April 13, 2026 - Last updated in NVD database

Technical Details for CVE-2026-6197

Vulnerability Analysis

This vulnerability falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), which encompasses buffer overflow conditions where data is written beyond allocated memory boundaries. The flaw specifically affects the wireless security settings configuration functionality of the Tenda F456 router.

The vulnerable function formWrlsafeset processes the mit_ssid parameter without adequate bounds checking. When an attacker supplies an oversized input value for the SSID parameter, the function writes beyond the allocated stack buffer, corrupting adjacent memory regions. This memory corruption can be leveraged to overwrite critical program control data, including return addresses and function pointers.

The network attack vector allows remote exploitation without requiring physical access to the device, making this vulnerability particularly dangerous for internet-exposed routers.

Root Cause

The root cause of this vulnerability is insufficient input validation and bounds checking in the formWrlsafeset function when processing the mit_ssid argument. The function fails to verify that the input length does not exceed the size of the destination buffer before performing the copy operation, resulting in a classic stack-based buffer overflow condition.

Attack Vector

The attack can be executed remotely over the network by sending a crafted HTTP request to the /goform/AdvSetWrlsafeset endpoint. An authenticated attacker can submit a maliciously long value for the mit_ssid parameter, triggering the buffer overflow. The exploitation requires low-privilege authenticated access to the router's web management interface.

The attacker sends an HTTP POST request to the vulnerable endpoint with an oversized mit_ssid parameter value. The formWrlsafeset function copies this value to a fixed-size stack buffer without proper length validation, causing the overflow. Depending on the payload, this can result in code execution, denial of service, or device compromise. For detailed technical information, refer to the GitHub vulnerability documentation.

Detection Methods for CVE-2026-6197

Indicators of Compromise

• Unexpected HTTP POST requests to /goform/AdvSetWrlsafeset with abnormally long mit_ssid parameter values
• Router crashes, reboots, or unresponsive behavior following web interface access
• Unusual outbound network traffic from the router indicating potential compromise
• Modified router configuration settings or unauthorized administrative accounts

Detection Strategies

• Deploy network intrusion detection rules to monitor HTTP traffic to Tenda router management interfaces for oversized parameter values
• Implement web application firewall rules to block requests with excessively long SSID parameter values
• Monitor router system logs for crash events or memory corruption indicators
• Perform periodic firmware version audits to identify vulnerable Tenda F456 devices running version 1.0.0.5

Monitoring Recommendations

• Enable logging on network perimeter devices for traffic destined to router management ports
• Implement alerting for repeated failed authentication attempts followed by successful access to the router web interface
• Deploy SentinelOne Singularity for network device monitoring to detect exploitation attempts and anomalous device behavior
• Establish baseline network behavior for IoT devices to identify deviations indicative of compromise

How to Mitigate CVE-2026-6197

Immediate Actions Required

• Restrict access to the router's web management interface to trusted IP addresses only
• Disable remote management access from the WAN interface if not required
• Implement network segmentation to isolate vulnerable routers from critical network assets
• Monitor the Tenda official website for security updates and firmware patches

Patch Information

As of the last update on April 13, 2026, no official patch has been released by Tenda for this vulnerability. Organizations should monitor Tenda's official channels for firmware updates and apply patches as soon as they become available. The vulnerability details have been submitted to VulDB and are documented in the VulDB vulnerability entry.

Workarounds

• Configure firewall rules to restrict access to port 80/443 on the router's management interface to authorized administrator IPs only
• Enable strong authentication mechanisms and change default credentials on the device
• Consider replacing affected devices with alternative router hardware if patches are not forthcoming
• Place vulnerable routers behind a separate firewall or network access control device

# Example firewall rules to restrict management interface access (implement on upstream firewall)
# Block external access to router management interface
iptables -A FORWARD -d <router_ip> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <router_ip> -p tcp --dport 443 -j DROP

# Allow only trusted management IPs
iptables -I FORWARD -s <trusted_admin_ip> -d <router_ip> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s <trusted_admin_ip> -d <router_ip> -p tcp --dport 443 -j ACCEPT