CVE-2026-4491 is a stack-based buffer overflow vulnerability identified in the Tenda A18 Pro router firmware version 02.03.02.28. The vulnerability resides in the fromSetIpMacBind function, which processes requests to the /goform/SetIpMacBind endpoint. By carefully crafting the argument list sent to this function, an attacker can overflow a stack buffer, potentially overwriting the return address or other control data on the stack. This can lead to arbitrary code execution on the device with elevated privileges, as the router firmware typically runs with high system privileges. The vulnerability is remotely exploitable without requiring authentication or user interaction, making it highly accessible to attackers scanning for vulnerable devices on the internet. The CVSS 4.0 score of 8.7 reflects the critical nature of this flaw, with network attack vector, low attack complexity, no privileges required, and no user interaction needed. The vulnerability impacts the device’s confidentiality, integrity, and availability, as an attacker could take full control of the router, intercept or manipulate network traffic, or disrupt network services. Although no exploits have been observed in the wild yet, the public disclosure of the exploit code increases the likelihood of exploitation attempts. No official patches or mitigation instructions have been provided by the vendor at the time of this report, increasing the urgency for organizations to implement interim protective measures.

The exploitation of CVE-2026-4491 can have severe consequences for organizations and individuals using the Tenda A18 Pro router. Attackers gaining control over the router can intercept, modify, or redirect network traffic, leading to data breaches and loss of confidentiality. They can also disrupt network availability by causing device crashes or reboots. Furthermore, compromised routers can serve as footholds for lateral movement within internal networks or as platforms for launching further attacks such as distributed denial-of-service (DDoS). Given the router’s role as a network gateway, the impact extends beyond the device itself to all connected systems. The lack of authentication and user interaction requirements lowers the barrier for exploitation, increasing the risk of widespread attacks. Organizations relying on this router model, especially in critical infrastructure, small and medium enterprises, and home networks, face significant risks if the vulnerability is not addressed promptly.

1. Immediate mitigation should include isolating the affected Tenda A18 Pro devices from untrusted networks, especially the internet, to reduce exposure. 2. Network administrators should implement strict firewall rules to block access to the /goform/SetIpMacBind endpoint or restrict access to trusted management IPs only. 3. Monitor network traffic for unusual requests targeting the vulnerable endpoint and implement intrusion detection/prevention systems (IDS/IPS) signatures specific to this exploit. 4. If possible, disable remote management features on the router to prevent external exploitation. 5. Regularly check for firmware updates from Tenda and apply official patches as soon as they become available. 6. Consider replacing vulnerable devices with models from vendors with a stronger security track record if patches are not forthcoming. 7. Conduct network segmentation to limit the impact of a compromised router on critical systems. 8. Educate users and administrators about the risks and signs of exploitation to enable rapid incident response.