CVE-2025-11326 is a stack-based buffer overflow vulnerability identified in the Tenda AC18 router firmware version 15.03.05.19(6318). The flaw exists in the handling of the wifi_chkHz parameter within the /goform/WifiMacFilterSet endpoint. An attacker can remotely send a specially crafted request manipulating this argument to overflow the stack buffer, potentially overwriting control data such as return addresses. This can lead to arbitrary code execution with the privileges of the router's web management service. The vulnerability requires no authentication or user interaction, making it highly exploitable remotely over the network. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P) indicates network attack vector, low attack complexity, no authentication, and high impact on confidentiality, integrity, and availability. Although no active exploitation has been reported, the availability of proof-of-concept exploits increases the likelihood of future attacks. The vulnerability affects a widely deployed consumer and SMB router model, which is often used in home and small office networks, potentially serving as a foothold for attackers to pivot into larger organizational networks. The lack of official patches at the time of disclosure further elevates the risk. This vulnerability underscores the importance of secure coding practices in embedded device firmware and the need for timely patch management.

For European organizations, exploitation of this vulnerability could lead to full compromise of affected Tenda AC18 routers, enabling attackers to intercept, manipulate, or disrupt network traffic. This can result in unauthorized access to internal networks, data breaches, disruption of business operations, and potential lateral movement to more critical systems. Given the router's role as a network gateway, attackers could establish persistent backdoors or launch denial-of-service attacks. Small and medium enterprises, as well as home offices relying on these routers, are particularly vulnerable due to potentially weaker network defenses. The impact extends to confidentiality, integrity, and availability of organizational data and services. Additionally, critical infrastructure sectors using these devices could face operational disruptions. The public availability of exploit code increases the urgency for mitigation to prevent widespread exploitation across European networks.

1. Immediately monitor Tenda's official channels for firmware updates addressing CVE-2025-11326 and apply patches as soon as they become available. 2. Until patches are released, restrict remote access to the router's management interface by disabling WAN-side administration and limiting access to trusted IP addresses. 3. Implement network segmentation to isolate vulnerable routers from critical systems and sensitive data. 4. Employ intrusion detection/prevention systems (IDS/IPS) to monitor and block suspicious traffic targeting the /goform/WifiMacFilterSet endpoint. 5. Regularly audit router configurations and logs for signs of exploitation attempts or unauthorized changes. 6. Educate users and administrators about the risks of this vulnerability and the importance of timely updates. 7. Consider replacing vulnerable devices with models from vendors with stronger security track records if patching is delayed or unavailable. 8. Use strong, unique passwords for router administration to reduce risk of privilege escalation in case of partial exploitation.