CVE-2026-3804 identifies a stack-based buffer overflow vulnerability in the Tenda i3 router firmware version 1.0.0.6(2204). The vulnerability resides in the formWifiMacFilterSet function, specifically in the /goform/WifiMacFilterSet web endpoint, which processes the 'index' argument. Improper validation or sanitization of this argument allows an attacker to overflow a buffer on the stack, potentially overwriting the return address or other control data. This flaw can be exploited remotely over the network without requiring authentication or user interaction, making it highly accessible to attackers. Successful exploitation could allow arbitrary code execution with elevated privileges on the device, leading to full compromise of the router. This could enable attackers to intercept, modify, or disrupt network traffic, pivot into internal networks, or launch further attacks. The CVSS v4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with the ease of exploitation and lack of required privileges or user interaction. Although no active exploitation has been reported, the public availability of an exploit increases the urgency for mitigation. The vulnerability affects a widely deployed consumer and small business router model, which may be present in various countries, especially where Tenda has market penetration. No official patches or firmware updates have been linked yet, but mitigation strategies should focus on limiting exposure and monitoring for attack attempts.

The impact of CVE-2026-3804 is significant for organizations and individuals using the Tenda i3 router model 1.0.0.6(2204). Exploitation can lead to full compromise of the device, allowing attackers to execute arbitrary code with elevated privileges. This can result in interception and manipulation of network traffic, loss of confidentiality of sensitive data, disruption of network availability, and potential lateral movement into internal networks. For enterprises relying on these routers for network connectivity, this could lead to data breaches, service outages, and damage to reputation. The vulnerability's remote exploitability without authentication or user interaction increases the risk of automated attacks and worm-like propagation. The public release of an exploit further elevates the threat level, as less skilled attackers can leverage it. Given the router's role as a network gateway, successful exploitation could undermine the security posture of entire organizations or home networks, making timely mitigation critical.

1. Immediately restrict remote access to the router's management interface by disabling WAN-side administration or limiting it to trusted IP addresses. 2. Implement network segmentation to isolate vulnerable devices from critical network assets, reducing potential lateral movement. 3. Monitor network traffic for unusual requests targeting /goform/WifiMacFilterSet or anomalous patterns indicative of buffer overflow attempts. 4. Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts against this vulnerability. 5. Regularly check for and apply official firmware updates from Tenda addressing this vulnerability once released. 6. If firmware updates are not yet available, consider replacing vulnerable devices with models from vendors with timely security support. 7. Educate network administrators about this vulnerability and the importance of limiting device exposure to untrusted networks. 8. Use network access control (NAC) to enforce device compliance and restrict unauthorized devices from connecting to sensitive networks.