CVE-2026-5155: Tenda CH22 Buffer Overflow Vulnerability

CVE-2026-5155 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda CH22 firmware version 1.0.0.1. This vulnerability exists in the fromAdvSetWan function within the /goform/AdvSetWan component, specifically in the Parameter Handler. By manipulating the wanmode argument, an attacker can trigger a stack-based buffer overflow condition. This vulnerability can be exploited remotely over the network, and a proof-of-concept exploit has been made publicly available.

Critical Impact

Remote attackers with low privileges can exploit this stack-based buffer overflow to potentially achieve code execution on affected Tenda CH22 devices, compromising the confidentiality, integrity, and availability of the network infrastructure.

Affected Products

• Tenda CH22 Firmware version 1.0.0.1
• Tenda CH22 Hardware Device

Discovery Timeline

• 2026-03-30 - CVE-2026-5155 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-5155

Vulnerability Analysis

This vulnerability is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-787 (Out-of-bounds Write). The flaw resides in the fromAdvSetWan function, which handles WAN configuration parameters submitted via the web-based management interface at /goform/AdvSetWan.

When processing the wanmode parameter, the function fails to properly validate the length of user-supplied input before copying it to a fixed-size stack buffer. This allows an attacker to supply a specially crafted, oversized value that overwrites adjacent memory on the stack, including return addresses and other critical control data.

The vulnerability is network-accessible and requires only low-level authentication to exploit, making it particularly dangerous for devices exposed to the internet or untrusted networks. Successful exploitation could allow an attacker to execute arbitrary code with the privileges of the web server process, potentially leading to full device compromise.

Root Cause

The root cause is insufficient input validation in the fromAdvSetWan function when handling the wanmode parameter. The code copies user-supplied data directly to a stack-allocated buffer without verifying that the input length does not exceed the buffer's capacity. This classic buffer overflow condition enables memory corruption when maliciously crafted input is submitted.

Attack Vector

The attack vector is network-based, targeting the web management interface of the Tenda CH22 router. An attacker can craft a malicious HTTP POST request to the /goform/AdvSetWan endpoint, supplying an oversized wanmode parameter value designed to overflow the stack buffer and overwrite critical memory regions.

The exploitation mechanism involves sending a POST request to the vulnerable endpoint with a payload structured to trigger the overflow. Technical details and proof-of-concept code can be found in the GitHub PoC Repository.

Detection Methods for CVE-2026-5155

Indicators of Compromise

• Unusual HTTP POST requests to /goform/AdvSetWan with abnormally large wanmode parameter values
• Unexpected device reboots or crashes indicating potential exploitation attempts
• Anomalous network traffic originating from the router to external command and control infrastructure
• Modified firmware or configuration files on the device

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests targeting /goform/AdvSetWan with oversized parameters
• Monitor web server logs on network devices for repeated requests to vulnerable endpoints
• Deploy SentinelOne Singularity platform for behavioral analysis of IoT/network devices where agent deployment is supported
• Utilize network traffic analysis tools to detect exploitation attempts and post-compromise lateral movement

Monitoring Recommendations

• Enable logging on all Tenda CH22 devices and forward logs to a centralized SIEM for analysis
• Set up alerts for authentication failures followed by configuration change attempts
• Monitor for firmware modification attempts or unauthorized administrative access
• Implement network segmentation to isolate management interfaces from untrusted networks

How to Mitigate CVE-2026-5155

Immediate Actions Required

• Restrict access to the router's web management interface to trusted internal networks only
• Implement firewall rules to block external access to port 80/443 on the device management interface
• Review device logs for evidence of exploitation attempts
• Consider isolating affected devices until a vendor patch is available

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Administrators should monitor the Tenda Security Page for firmware updates addressing CVE-2026-5155. Additional technical information is available through VulDB #354187.

Workarounds

• Disable remote management capabilities on the Tenda CH22 device if not required
• Place the router behind an additional firewall or VPN to restrict management access
• Implement network-level access controls to limit which hosts can reach the management interface
• Consider replacing vulnerable devices with alternatives that have a stronger security track record until patches become available

# Recommended firewall rule to block external access to management interface
# Example using iptables on an upstream Linux firewall
iptables -A FORWARD -d <TENDA_CH22_IP> -p tcp --dport 80 -j DROP
iptables -A FORWARD -d <TENDA_CH22_IP> -p tcp --dport 443 -j DROP

# Allow management access only from trusted admin subnet
iptables -I FORWARD -s <ADMIN_SUBNET> -d <TENDA_CH22_IP> -p tcp --dport 80 -j ACCEPT
iptables -I FORWARD -s <ADMIN_SUBNET> -d <TENDA_CH22_IP> -p tcp --dport 443 -j ACCEPT