CVE-2026-3799 is a stack-based buffer overflow vulnerability identified in the Tenda i3 router firmware version 1.0.0.6(2204). The vulnerability resides in the formSetCfm function, specifically in the handling of the funcpara1 parameter within the /goform/setcfm endpoint. Improper validation or sanitization of this input allows an attacker to overflow the stack buffer, which can lead to arbitrary code execution or denial of service. The vulnerability is remotely exploitable over the network without requiring user interaction or elevated privileges, making it highly accessible to attackers. The CVSS v4.0 score of 8.7 reflects its high severity, with attack vector being network-based, low attack complexity, no privileges required, and no user interaction needed. The impact covers confidentiality, integrity, and availability, as successful exploitation could allow attackers to execute arbitrary code, disrupt device operation, or gain unauthorized access to network traffic. Although no confirmed active exploitation in the wild has been reported, a public exploit is available, increasing the urgency for mitigation. The lack of official patches at the time of publication necessitates alternative defensive measures. This vulnerability primarily affects Tenda i3 routers, which are widely used in residential and small business environments, particularly in Asia-Pacific regions. The exploit targets a web management interface endpoint, which is commonly exposed in many deployments, increasing the attack surface. Organizations relying on these devices should prioritize detection and containment strategies while awaiting vendor patches.

The impact of CVE-2026-3799 is significant for organizations using Tenda i3 routers. Successful exploitation can lead to remote code execution, allowing attackers to take full control of the device. This compromises the confidentiality of network traffic passing through the router, potentially exposing sensitive data. Integrity is at risk as attackers could modify device configurations or inject malicious payloads into network communications. Availability may be disrupted through denial-of-service conditions caused by the buffer overflow. Given that these routers often serve as gateways for home and small business networks, attackers could leverage compromised devices as footholds for lateral movement, launching further attacks against internal systems or using them as part of botnets. The ease of exploitation without authentication or user interaction increases the likelihood of widespread attacks once exploit code is leveraged. The absence of patches means that affected organizations remain vulnerable until mitigations are applied, elevating the risk of operational disruption and data breaches.

1. Immediately restrict access to the router’s management interface, especially the /goform/setcfm endpoint, by implementing network segmentation and firewall rules to limit exposure to trusted IP addresses only. 2. Disable remote management features if not strictly necessary to reduce the attack surface. 3. Monitor network traffic for unusual requests targeting the /goform/setcfm endpoint or anomalous patterns indicative of buffer overflow exploitation attempts. 4. Employ intrusion detection and prevention systems (IDS/IPS) with updated signatures capable of detecting attempts to exploit this specific vulnerability. 5. Regularly audit and update router firmware; although no patch is currently available, maintain close communication with Tenda for official updates or advisories. 6. Consider replacing vulnerable devices with models from vendors with more robust security update practices if immediate patching is not feasible. 7. Implement network-level anomaly detection to identify compromised devices exhibiting suspicious behavior post-exploitation. 8. Educate users and administrators about the risks of exposing management interfaces to the internet and enforce strong network security policies.