Executive Summary

CVE-2026-5204 is a stack-based buffer overflow vulnerability found in the Tenda CH22 device, version 1.0.0.1. It exists in the function formWebTypeLibrary of the /goform/webtypelibrary component, specifically in the handling of the user-supplied parameter "webSiteId".

The vulnerability occurs because the "webSiteId" parameter is copied into a buffer using the strcat function without any bounds checking, which can overflow the stack-based buffer named "dest".

An attacker can exploit this remotely by sending a crafted HTTP POST request with an excessively long "webSiteId" value to the endpoint "/goform/webtypelibrary", potentially causing a denial of service or enabling remote code execution.

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Impact Analysis

This vulnerability can have serious impacts including causing a denial of service (DoS) on the affected Tenda CH22 device or allowing an attacker to execute arbitrary code remotely.

Remote code execution could enable attackers to take control of the device, potentially leading to further network compromise or disruption of services.

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Detection Guidance

This vulnerability can be detected by monitoring for suspicious HTTP POST requests sent to the endpoint "/goform/webtypelibrary" that contain an unusually long or crafted "webSiteId" parameter. Such requests may indicate attempts to exploit the stack-based buffer overflow.

A practical detection method is to capture and analyze network traffic targeting the Tenda CH22 device, specifically looking for POST requests with the "webSiteId" parameter in the payload.

Example commands to detect potential exploitation attempts include:

• Using tcpdump to capture relevant HTTP POST requests: tcpdump -i <interface> -A 'tcp port 80 and (((ip dst <device_ip>) and (tcp[32:4] = 0x504f5354)))'
• Using grep or similar tools on captured traffic or logs to search for "webSiteId" parameters with unusually long values.
• Using curl or similar tools to test the endpoint with crafted payloads to verify if the device is vulnerable.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable endpoint "/goform/webtypelibrary" by implementing network-level controls such as firewall rules to block unauthorized or external access.

Additionally, monitoring and filtering HTTP POST requests to detect and block those containing suspiciously long "webSiteId" parameters can help prevent exploitation.

If possible, update the device firmware to a version that patches this vulnerability, as the issue is caused by improper bounds checking in the affected firmware version 1.0.0.1.

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Compliance Impact

The provided information does not specify any direct impact of the CVE-2026-5204 vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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