CVE-2026-3801 identifies a stack-based buffer overflow vulnerability in the Tenda i3 router firmware version 1.0.0.6(2204). The flaw resides in the formSetAutoPing function within the /goform/setAutoPing endpoint, which processes the ping1 and ping2 parameters. Improper handling of these input arguments allows an attacker to overflow the stack buffer, potentially overwriting return addresses or other control data. This vulnerability is remotely exploitable over the network without requiring authentication or user interaction, increasing its severity and ease of exploitation. The CVSS v4.0 score of 8.7 reflects high impact on confidentiality, integrity, and availability, with low attack complexity and no privileges required. Exploitation could lead to arbitrary code execution, enabling attackers to take full control of the device, disrupt network operations, or pivot into internal networks. Although no confirmed in-the-wild exploitation has been reported, a public exploit is available, increasing the risk of future attacks. The vulnerability affects a specific firmware version, and no official patches have been documented yet, necessitating urgent attention from users and administrators of Tenda i3 devices.

The impact of CVE-2026-3801 is significant for organizations relying on Tenda i3 routers, particularly in environments where these devices serve as critical network gateways or infrastructure components. Successful exploitation can lead to full device compromise, allowing attackers to execute arbitrary code, disrupt network connectivity, intercept or manipulate traffic, and potentially use the device as a foothold for lateral movement within internal networks. This can result in data breaches, service outages, and loss of network integrity. The remote, unauthenticated nature of the exploit increases the attack surface, making it feasible for attackers to target vulnerable devices at scale. Organizations with limited network segmentation or outdated device inventories face heightened risk. The absence of patches further exacerbates the threat, potentially leading to widespread exploitation if attackers deploy automated scanning and exploitation tools.

To mitigate CVE-2026-3801, organizations should first verify if they are using Tenda i3 devices running firmware version 1.0.0.6(2204). Immediate steps include isolating affected devices from untrusted networks and restricting access to the /goform/setAutoPing endpoint via firewall rules or access control lists. Network segmentation should be enforced to limit exposure of vulnerable devices. Monitoring network traffic for unusual requests targeting the setAutoPing endpoint can help detect exploitation attempts. If possible, disable the auto-ping feature or related services until a vendor patch is available. Organizations should engage with Tenda support to obtain firmware updates or security advisories. Additionally, deploying intrusion prevention systems (IPS) with signatures targeting this vulnerability can help block exploit attempts. Regularly updating device inventories and applying strict network access policies will reduce the attack surface. Finally, consider replacing vulnerable devices with models that have active security support if patches are delayed.