CVE-2026-4960: Tenda AC6 Buffer Overflow Vulnerability

CVE-2026-4960 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda AC6 wireless router firmware version 15.03.05.16. The vulnerability exists in the fromWizardHandle function within the /goform/WizardHandle endpoint of the POST Request Handler component. An attacker can exploit this flaw by manipulating the WANT or WANS arguments, resulting in a stack-based buffer overflow that can be triggered remotely over the network.

Critical Impact

This vulnerability allows remote attackers with low privileges to potentially achieve complete compromise of affected Tenda AC6 routers, impacting confidentiality, integrity, and availability of the device and connected network. The exploit has been publicly disclosed and may be utilized by threat actors.

Affected Products

• Tenda AC6 Firmware version 15.03.05.16
• Tenda AC6 Hardware version 1.0

Discovery Timeline

• 2026-03-27 - CVE-2026-4960 published to NVD
• 2026-03-31 - Last updated in NVD database

Technical Details for CVE-2026-4960

Vulnerability Analysis

This vulnerability is classified as a stack-based buffer overflow (CWE-787: Out-of-bounds Write, CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The vulnerable function fromWizardHandle processes POST requests to the /goform/WizardHandle endpoint without proper bounds checking on user-supplied input.

When processing the WANT or WANS parameters, the function fails to validate the length of input data before copying it to a fixed-size stack buffer. This allows an attacker to overflow the buffer boundaries and potentially overwrite adjacent memory, including the return address on the stack.

Root Cause

The root cause is improper input validation in the fromWizardHandle function. The firmware does not implement adequate length checks when handling the WANT and WANS arguments from HTTP POST requests. This lack of boundary enforcement allows oversized input to overflow the stack buffer, corrupting adjacent memory regions.

Attack Vector

The attack is network-accessible and can be executed remotely by sending a specially crafted HTTP POST request to the /goform/WizardHandle endpoint on the affected Tenda AC6 router. The attacker requires low-level privileges (authentication to the router's web interface) but no user interaction is needed for exploitation.

An attacker would craft a malicious POST request with an oversized WANT or WANS parameter value designed to overflow the stack buffer. Successful exploitation could result in arbitrary code execution with the privileges of the web server process, potentially leading to full device compromise.

Technical details and additional analysis are available in the Notion Vulnerability Document.

Detection Methods for CVE-2026-4960

Indicators of Compromise

• Unusual HTTP POST requests to /goform/WizardHandle with abnormally large WANT or WANS parameter values
• Unexpected router reboots or crashes following web interface access
• Suspicious processes or network connections originating from the router
• Modified router configuration or unauthorized administrative accounts

Detection Strategies

• Monitor network traffic for HTTP POST requests to /goform/WizardHandle endpoints containing oversized parameters
• Implement IDS/IPS signatures to detect buffer overflow attempts targeting Tenda AC6 routers
• Review router access logs for repeated failed requests or unusual parameter patterns
• Deploy network segmentation to isolate IoT devices and routers from critical network segments

Monitoring Recommendations

• Enable logging on network firewalls to capture traffic destined for Tenda router management interfaces
• Implement network monitoring for anomalous traffic patterns to port 80/443 on router IP addresses
• Consider deploying a Web Application Firewall (WAF) in front of exposed router interfaces
• Regularly audit device firmware versions to identify vulnerable deployments

How to Mitigate CVE-2026-4960

Immediate Actions Required

• Restrict access to the router's web management interface to trusted networks only
• Disable remote management features if not required
• Implement strong network segmentation to limit exposure of vulnerable devices
• Monitor for any available firmware updates from Tenda

Patch Information

As of the last update on 2026-03-31, no official patch from Tenda has been documented in the available CVE data. Organizations should monitor the Tenda Official Website for security advisories and firmware updates. Additional vulnerability tracking information is available at VulDB #353837.

Workarounds

• Disable the web management interface on WAN-facing ports
• Configure firewall rules to block external access to management ports (typically port 80/443 on the router)
• Use VPN access for remote administration instead of exposing the management interface directly
• Consider replacing affected devices with alternatives that receive active security support

# Example firewall rule to restrict access to router management interface
# Block external access to Tenda router web interface (adjust IP as needed)
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin subnet
iptables -A FORWARD -s 192.168.10.0/24 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT