CVE-2022-40101 is a high-severity vulnerability identified in the Tenda i9 router firmware version 1.0.0.8(3828). The vulnerability arises from a buffer overflow condition in the formWifiMacFilterSet function. This function is likely responsible for managing MAC address filtering settings on the device's Wi-Fi interface. An attacker can exploit this vulnerability by sending a specially crafted string to the vulnerable function, causing a buffer overflow. This overflow can lead to a Denial of Service (DoS) condition, effectively disrupting the normal operation of the router. The vulnerability does not require any authentication or user interaction, and it can be exploited remotely over the network (AV:N). The attack complexity is low (AC:L), meaning it is straightforward to exploit. The vulnerability impacts availability only (A:H), with no direct impact on confidentiality or integrity. No known exploits are currently reported in the wild, and no patches or vendor advisories have been linked. The underlying weakness is classified as CWE-787, which corresponds to out-of-bounds write errors, a common cause of buffer overflows. Given the nature of the vulnerability, successful exploitation could cause the router to crash or reboot, leading to network downtime and loss of connectivity for users relying on the device.

For European organizations, the impact of this vulnerability can be significant, especially for small and medium enterprises (SMEs) or home office environments that utilize Tenda i9 routers. A successful DoS attack could disrupt internet access, internal communications, and critical business operations dependent on network connectivity. This could lead to productivity losses and potential secondary impacts if network-dependent security systems or monitoring tools are affected. Although the vulnerability does not allow data theft or manipulation, the loss of availability can be exploited as part of a broader attack strategy, such as diverting attention while other attacks are conducted. Additionally, if attackers use this vulnerability to cause repeated outages, it could degrade trust in network infrastructure reliability. The lack of authentication requirement and ease of exploitation increase the risk profile, as attackers can launch attacks remotely without prior access. Organizations with remote or distributed workforces relying on these routers are particularly vulnerable to service interruptions.

To mitigate this vulnerability, European organizations should first identify whether they are using the Tenda i9 router with the affected firmware version 1.0.0.8(3828). If so, immediate steps should include isolating these devices from untrusted networks and restricting access to management interfaces. Network segmentation can limit exposure. Since no official patch is currently available, organizations should monitor vendor communications for firmware updates addressing this issue and apply them promptly once released. As a temporary workaround, disabling MAC filtering features or any web interface components related to formWifiMacFilterSet may reduce attack surface, if feasible. Employing network-level protections such as intrusion detection/prevention systems (IDS/IPS) to detect and block suspicious traffic patterns targeting the router's management interfaces can also help. Regular network monitoring and anomaly detection should be enhanced to quickly identify potential exploitation attempts. Finally, organizations should consider replacing vulnerable routers with devices from vendors that provide timely security updates and have a strong security posture.