CVE-2026-2202: Tenda AC8 Buffer Overflow Vulnerability

CVE-2026-2202 Overview

A buffer overflow vulnerability has been identified in the Tenda AC8 router firmware version 16.03.33.05. The vulnerability exists in the fromSetWifiGusetBasic function within the /goform/WifiGuestSet endpoint of the httpd component. Remote attackers can exploit this vulnerability by manipulating the shareSpeed argument, potentially leading to arbitrary code execution or denial of service on affected devices. The exploit for this vulnerability is publicly available, increasing the risk of active exploitation.

Critical Impact

Remote attackers can exploit this buffer overflow vulnerability over the network to potentially execute arbitrary code or crash affected Tenda AC8 routers, compromising network security and availability.

Affected Products

• Tenda AC8 Firmware version 16.03.33.05
• Tenda AC8 Hardware

Discovery Timeline

• 2026-02-09 - CVE-2026-2202 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-2202

Vulnerability Analysis

This vulnerability affects the Tenda AC8 wireless router's web management interface. The root cause is improper buffer boundary checks in the fromSetWifiGusetBasic function, which handles guest WiFi configuration requests. When processing the shareSpeed parameter submitted via POST requests to /goform/WifiGuestSet, the function fails to validate the length of user-supplied input before copying it into a fixed-size buffer.

The vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-120 (Buffer Copy without Checking Size of Input). An attacker can remotely trigger this vulnerability without user interaction, though low-level privileges are required. Successful exploitation could allow attackers to overwrite adjacent memory locations, potentially gaining control of program execution flow.

Root Cause

The vulnerability stems from classic insecure memory handling practices in the embedded firmware. The fromSetWifiGusetBasic function uses unsafe string copy operations that do not perform bounds checking on the shareSpeed parameter. When an attacker supplies an overly long value for this parameter, the function writes beyond the allocated buffer boundaries, corrupting adjacent stack or heap memory depending on the implementation.

Attack Vector

The attack is network-based and targets the httpd web server running on the Tenda AC8 router. An authenticated attacker with low-level privileges can craft a malicious HTTP POST request to the /goform/WifiGuestSet endpoint with an oversized shareSpeed value. The attack does not require user interaction and can be launched remotely against any accessible Tenda AC8 device running the vulnerable firmware version.

The exploitation mechanism involves sending a specially crafted request that overflows the buffer allocated for the shareSpeed parameter. Technical details and proof-of-concept information are available in the GitHub PoC Documentation.

Detection Methods for CVE-2026-2202

Indicators of Compromise

• Unexpected crashes or reboots of Tenda AC8 routers without administrator action
• Abnormally large HTTP POST requests to /goform/WifiGuestSet endpoint
• Suspicious network traffic patterns targeting router management interfaces
• Unusual modifications to router configuration or firmware

Detection Strategies

• Monitor HTTP traffic for oversized shareSpeed parameter values in requests to /goform/WifiGuestSet
• Implement network intrusion detection rules to identify buffer overflow exploitation attempts against Tenda devices
• Review router access logs for repeated authentication attempts followed by configuration endpoint access
• Deploy web application firewalls with rules to block malformed requests to router management interfaces

Monitoring Recommendations

• Enable comprehensive logging on network perimeter devices monitoring traffic to/from Tenda routers
• Configure alerts for any external access attempts to router management interfaces (port 80/443)
• Implement network segmentation to isolate IoT devices including routers from critical network segments
• Regularly audit router configurations and firmware versions against known vulnerable versions

How to Mitigate CVE-2026-2202

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Disable remote management features if not required
• Implement strong access controls and change default credentials on all Tenda AC8 devices
• Consider placing affected devices behind a properly configured firewall that blocks external management access

Patch Information

As of the last update on 2026-02-10, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for firmware updates addressing this issue. Additional technical information is available through VulDB #344905.

Workarounds

• Disable the guest WiFi feature if not operationally required until a patch is available
• Use network access control lists (ACLs) to restrict which IP addresses can access the router management interface
• Implement a web application firewall or reverse proxy that can filter and validate input to the vulnerable endpoint
• Consider replacing affected devices with alternative hardware if critical security requirements cannot be met

# Example: Restrict management interface access via iptables on upstream firewall
# Block external access to router management on port 80
iptables -A FORWARD -d <ROUTER_IP> -p tcp --dport 80 -j DROP

# Allow only trusted management subnet
iptables -I FORWARD -s 192.168.1.0/24 -d <ROUTER_IP> -p tcp --dport 80 -j ACCEPT