Executive Summary

CVE-2026-3973 is a stack-based buffer overflow vulnerability found in the Tenda W3 router, version 1.0.0.3(2204). It affects the formSetAutoPing function accessed via the /goform/setAutoPing HTTP endpoint. The vulnerability arises because the POST parameters ping1 and ping2 are copied into fixed-size stack buffers without proper length validation. An attacker can send a specially crafted POST request with an excessively long ping1 or ping2 parameter, causing a buffer overflow.

This overflow can lead to stack corruption, which may cause the device to crash (denial of service) or potentially allow an attacker to execute arbitrary code remotely. Exploitation does not require physical or local access and can be performed remotely.

Useful 0 Not Useful 0

Impact Analysis

This vulnerability can impact you by allowing a remote attacker to cause a denial of service or execute arbitrary code on the affected Tenda W3 router. This means the attacker could crash the device, disrupting network connectivity, or take control of the router to perform malicious actions.

Because the exploit can be carried out remotely without authentication, it poses a significant security risk to the confidentiality, integrity, and availability of the device and potentially the network it supports.

Useful 0 Not Useful 0

Compliance Impact

I don't know

Useful 0 Not Useful 0

Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by monitoring for suspicious POST requests to the /goform/setAutoPing HTTP endpoint on Tenda W3 routers running firmware version 1.0.0.3(2204). Specifically, look for POST requests containing excessively long values in the ping1 or ping2 parameters, which are indicators of attempts to trigger the buffer overflow.'}, {'type': 'paragraph', 'content': 'A practical detection method is to capture network traffic and filter HTTP POST requests to /goform/setAutoPing, then inspect the length of the ping1 and ping2 parameters.'}, {'type': 'paragraph', 'content': 'Example commands to detect such attempts include:'}, {'type': 'list_item', 'content': "Using tcpdump to capture relevant HTTP POST requests: tcpdump -i <interface> -A 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep '/goform/setAutoPing'"}, {'type': 'list_item', 'content': 'Using curl to test the vulnerability by sending a crafted POST request with a large ping1 or ping2 parameter: curl -X POST http://<router-ip>/goform/setAutoPing -d \'linkEn=1&ping1=$(python3 -c "print(\'A\'*1000)")\''}, {'type': 'list_item', 'content': 'Using intrusion detection systems (IDS) or web application firewalls (WAF) to create rules that alert on unusually long ping1 or ping2 POST parameters targeting /goform/setAutoPing.'}] [1, 2, 4, 5]

Useful 0 Not Useful 0

Mitigation Strategies

Currently, there are no known countermeasures or official patches available for this vulnerability in the affected Tenda W3 firmware version 1.0.0.3(2204).

Immediate mitigation steps include:

• Restrict or block external access to the /goform/setAutoPing endpoint on the router by configuring firewall rules to prevent remote POST requests targeting this path.
• Disable or limit the use of the auto ping feature if possible, or set the linkEn parameter to 0 to avoid triggering the vulnerable code path.
• Monitor network traffic for exploitation attempts and respond by blocking offending IP addresses.
• Consider replacing the affected device with a different model or vendor that is not vulnerable.

Useful 0 Not Useful 0