CVE-2026-3801 identifies a critical stack-based buffer overflow vulnerability in the Tenda i3 router firmware version 1.0.0.6(2204). The vulnerability resides in the formSetAutoPing function, specifically in the /goform/setAutoPing endpoint, which processes the ping1 and ping2 parameters. Improper handling of these parameters allows an attacker to 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 accessible to attackers. The CVSS v4.0 score is 8.7 (high severity), reflecting the ease of exploitation and the significant impact on confidentiality, integrity, and availability. While no confirmed exploits in the wild have been reported, a public exploit is available, increasing the likelihood of exploitation. The affected product, Tenda i3, is a consumer and small office router, which may be deployed in various regions worldwide. The lack of an official patch link suggests that mitigation may currently rely on workarounds or vendor updates pending release. This vulnerability highlights the risks of insecure input validation in network device firmware and the importance of timely patching.

The impact of CVE-2026-3801 is substantial for organizations and individuals using the Tenda i3 router. Successful exploitation can lead to remote code execution, allowing attackers to gain control over the device, manipulate network traffic, or pivot into internal networks. This compromises confidentiality by exposing sensitive data, integrity by enabling unauthorized changes, and availability by causing device crashes or network outages. Small businesses and home users relying on Tenda i3 devices for internet connectivity and network security are particularly vulnerable. The exploitability without authentication or user interaction increases the attack surface, enabling widespread scanning and automated attacks. The presence of a public exploit further elevates the risk of rapid exploitation campaigns. Organizations with limited network segmentation or monitoring may face significant operational disruptions and potential data breaches. The vulnerability also poses risks to critical infrastructure if Tenda i3 devices are used in such environments, potentially impacting national security or essential services.

To mitigate CVE-2026-3801, organizations should first check for official firmware updates from Tenda addressing this vulnerability and apply them promptly once available. In the absence of an official patch, network administrators should implement the following specific measures: 1) Restrict access to the router's management interface by limiting it to trusted IP addresses and disabling remote management if not required. 2) Employ network segmentation to isolate vulnerable devices from critical systems and sensitive data. 3) Monitor network traffic for unusual requests targeting the /goform/setAutoPing endpoint or suspicious patterns indicative of exploitation attempts. 4) Use intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting buffer overflow attempts against Tenda devices. 5) Disable or restrict the auto-ping feature if configurable, reducing the attack surface. 6) Educate users about the risks of exposing network devices to the internet and encourage secure configuration practices. 7) Consider replacing vulnerable devices with models from vendors with a strong security track record if timely patches are unavailable. These targeted actions go beyond generic advice by focusing on access control, monitoring, and configuration hardening specific to this vulnerability.