CVE-2026-3973 is a stack-based buffer overflow vulnerability identified in the Tenda W3 router firmware version 1.0.0.3(2204). The vulnerability resides in the formSetAutoPing function, specifically in the POST parameter handler for the /goform/setAutoPing endpoint. By manipulating the ping1 and ping2 parameters, an attacker can overflow the stack buffer, potentially overwriting the return address or other control data on the stack. This can lead to arbitrary code execution or cause the device to crash, resulting in denial of service. The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, making it highly dangerous. The CVSS v4.0 base score is 8.7, reflecting the ease of exploitation and the high impact on confidentiality, integrity, and availability. Although no known exploits are currently active in the wild, the public disclosure of exploit details increases the likelihood of future attacks. The affected device is a consumer and small office router, which may be deployed in various home and enterprise environments. The lack of available patches at the time of disclosure means that mitigation relies on network-level controls and configuration changes until a firmware update is released.

The vulnerability allows remote attackers to execute arbitrary code or cause denial of service on affected Tenda W3 routers. Successful exploitation can compromise the confidentiality and integrity of network traffic passing through the device, potentially allowing attackers to intercept, modify, or disrupt communications. The availability of the device can also be impacted, leading to network outages or degraded performance. For organizations, this can result in loss of business continuity, exposure of sensitive data, and increased risk of lateral movement within internal networks. Given the router’s role as a gateway device, compromise could serve as a foothold for further attacks against connected systems. The absence of authentication requirements and user interaction lowers the barrier for attackers, increasing the threat level. The public disclosure of the exploit details further elevates the risk of widespread exploitation, especially in environments where firmware updates are not promptly applied.

1. Immediately isolate affected Tenda W3 devices from untrusted networks to reduce exposure. 2. Disable or restrict access to the /goform/setAutoPing endpoint if possible via device configuration or firewall rules. 3. Implement network segmentation to limit the impact of a compromised router on critical systems. 4. Monitor network traffic for unusual POST requests targeting /goform/setAutoPing or anomalous ping parameter values. 5. Apply any available firmware updates from Tenda as soon as they are released addressing this vulnerability. 6. If firmware updates are unavailable, consider replacing affected devices with models not impacted by this vulnerability. 7. Employ intrusion detection/prevention systems (IDS/IPS) with signatures targeting exploitation attempts of this vulnerability. 8. Educate network administrators about the vulnerability and ensure incident response plans include steps for compromised network devices. 9. Regularly audit router configurations and logs to detect signs of exploitation or unauthorized changes. 10. Limit remote management access to trusted IPs and use VPNs or secure channels where remote access is necessary.