CVE-2022-40865 is a critical heap overflow vulnerability identified in Tenda AC15 and AC18 routers running firmware version V15.03.05.19. The vulnerability exists within the function setSchedWifi, which processes requests sent to the endpoint /goform/openSchedWifi/. A heap overflow occurs when more data is written to a heap buffer than it can hold, potentially allowing an attacker to overwrite adjacent memory. This can lead to arbitrary code execution, denial of service, or system compromise. The vulnerability has a CVSS 3.1 base score of 9.8, indicating it is highly severe. The vector string (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) shows that the attack can be performed remotely over the network without any privileges or user interaction, and it impacts confidentiality, integrity, and availability to a high degree. The weakness is classified under CWE-787 (Out-of-bounds Write), which is a common cause of memory corruption issues. Although no known exploits are currently reported in the wild, the ease of exploitation and critical impact make this vulnerability a significant risk. The lack of available patches or vendor advisories at the time of publication increases the urgency for affected users to take protective measures. Given that Tenda routers are commonly used in home and small office environments, exploitation could allow attackers to gain control over network traffic, intercept sensitive data, or disrupt internet connectivity.

For European organizations, especially small and medium enterprises (SMEs) and home office users relying on Tenda AC15 and AC18 routers, this vulnerability poses a severe threat. Successful exploitation could lead to full compromise of the router, enabling attackers to intercept or manipulate network traffic, launch man-in-the-middle attacks, or pivot into internal networks. This could result in data breaches, intellectual property theft, disruption of business operations, and potential exposure of sensitive personal data protected under GDPR. The critical nature of the vulnerability means that attackers could remotely execute arbitrary code without authentication or user interaction, increasing the risk of widespread exploitation. Additionally, compromised routers could be enlisted into botnets, amplifying threats such as distributed denial-of-service (DDoS) attacks against European infrastructure. The impact is particularly concerning for organizations with limited IT security resources that may not regularly update or monitor their network devices.

Given the absence of official patches, European organizations should implement immediate compensating controls. First, isolate affected Tenda routers from critical internal networks and restrict remote management interfaces to trusted IP addresses only. Disable any unnecessary services or remote access features on the routers. Monitor network traffic for unusual patterns that may indicate exploitation attempts. Where possible, replace vulnerable Tenda AC15 and AC18 routers with models from vendors that provide timely security updates and have a strong security track record. Implement network segmentation to limit the impact of a compromised device. Regularly audit and update router firmware as soon as vendors release patches. Employ intrusion detection/prevention systems (IDS/IPS) to detect exploitation attempts targeting the /goform/openSchedWifi/ endpoint. Finally, educate users about the risks of using outdated network equipment and encourage proactive security hygiene.