CVE-2026-5204: Tenda CH22 Buffer Overflow Vulnerability

CVE-2026-5204 Overview

A stack-based buffer overflow vulnerability has been identified in Tenda CH22 firmware version 1.0.0.1. The vulnerability exists in the formWebTypeLibrary function within the /goform/webtypelibrary endpoint of the Parameter Handler component. Improper handling of the webSiteId argument 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 allows authenticated attackers to overflow the stack buffer through malicious input to the webSiteId parameter, potentially enabling remote code execution on affected Tenda CH22 devices.

Affected Products

• Tenda CH22 Firmware version 1.0.0.1
• Tenda CH22 Hardware

Discovery Timeline

• 2026-03-31 - CVE-2026-5204 published to NVD
• 2026-04-02 - Last updated in NVD database

Technical Details for CVE-2026-5204

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 firmware's web management interface, specifically within the formWebTypeLibrary function that processes HTTP requests sent to the /goform/webtypelibrary endpoint.

When processing the webSiteId parameter, the function fails to properly validate the length of user-supplied input before copying it into a fixed-size stack buffer. This oversight allows an attacker to supply an oversized value that exceeds the buffer's allocated memory space, overwriting adjacent stack memory including potentially critical data such as return addresses and saved registers.

The exploit details have been publicly disclosed, increasing the risk profile for organizations running affected firmware versions. The vulnerability can be exploited remotely over the network, requiring only low-privilege authentication to access the vulnerable endpoint.

Root Cause

The root cause of this vulnerability is insufficient input validation in the formWebTypeLibrary function. The code fails to enforce proper boundary checks on the webSiteId parameter before performing memory copy operations. Without adequate length validation, user-controlled data can overflow the destination stack buffer, corrupting adjacent memory regions and potentially hijacking program execution flow.

Attack Vector

The attack vector is network-based, targeting the web management interface of the Tenda CH22 router. An attacker with low-privilege access to the device's administrative interface can craft a malicious HTTP request to the /goform/webtypelibrary endpoint containing an oversized webSiteId parameter value. When processed by the vulnerable function, the oversized input triggers a stack-based buffer overflow.

The vulnerability can be exploited by sending a specially crafted POST request to the vulnerable endpoint. The malicious payload in the webSiteId parameter must exceed the expected buffer size to overflow the stack. Technical details and proof-of-concept information are available through the GitHub Vulnerability README.

Detection Methods for CVE-2026-5204

Indicators of Compromise

• Unusual HTTP POST requests to /goform/webtypelibrary with abnormally large webSiteId parameter values
• Unexpected device reboots or crashes indicating potential exploitation attempts
• Anomalous network traffic patterns targeting the router's web management interface
• Signs of unauthorized access or configuration changes on Tenda CH22 devices

Detection Strategies

• Implement network intrusion detection rules to identify HTTP requests with oversized parameters targeting /goform/webtypelibrary
• Monitor web server logs for repeated requests to the vulnerable endpoint with unusual payload sizes
• Deploy web application firewall (WAF) rules to block requests exceeding expected parameter lengths
• Use SentinelOne Singularity to detect anomalous behavior patterns on network devices

Monitoring Recommendations

• Enable verbose logging on Tenda CH22 devices to capture web management interface activity
• Implement network segmentation to limit exposure of router management interfaces
• Set up alerts for unexpected device behavior such as crashes, reboots, or configuration changes
• Regularly audit network traffic for signs of exploitation attempts against IoT devices

How to Mitigate CVE-2026-5204

Immediate Actions Required

• Restrict network access to the Tenda CH22 web management interface to trusted IP addresses only
• Disable remote management features if not required for operations
• Place affected devices behind a properly configured firewall
• Monitor for firmware updates from Tenda and apply patches as soon as they become available

Patch Information

At the time of publication, no official patch has been released by Tenda for this vulnerability. Organizations should monitor the Tenda Official Website for security updates and firmware releases addressing CVE-2026-5204. Additional vulnerability information can be found at VulDB #354332.

Workarounds

• Implement access control lists (ACLs) to restrict access to the /goform/webtypelibrary endpoint
• Deploy a reverse proxy or web application firewall to filter malicious requests before they reach the device
• Disable the web management interface and use alternative management methods if available
• Consider replacing affected devices with alternatives that receive regular security updates

# Configuration example - Restrict management interface access
# On upstream firewall or router, block external access to device management
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP