CVE-2022-44163 is a high-severity vulnerability affecting the Tenda AC21 router firmware version V16.03.08.15. The vulnerability arises from a buffer overflow condition in the function formSetMacFilterCfg. Buffer overflow vulnerabilities occur when a program writes more data to a buffer than it can hold, potentially overwriting adjacent memory. In this case, the overflow can be triggered remotely over the network without requiring any authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The vulnerability impacts availability (A:H) but does not affect confidentiality or integrity directly (C:N/I:N). Exploiting this flaw could allow an attacker to cause a denial of service (DoS) by crashing the device or potentially executing arbitrary code, depending on the router's memory protection mechanisms. The vulnerability is classified under CWE-787 (Out-of-bounds Write), a common and dangerous class of memory corruption bugs. No patches or official fixes have been linked or published yet, and there are no known exploits in the wild at this time. However, the ease of exploitation and the lack of required privileges make this a significant risk for affected devices. The Tenda AC21 is a consumer-grade Wi-Fi 6 router, commonly used in home and small office environments, which may also be deployed in some enterprise edge networks. The absence of vendor and product details beyond the model and firmware version limits the scope of precise technical attribution but does not diminish the threat posed by this vulnerability to affected devices.

For European organizations, the primary impact of this vulnerability lies in the potential disruption of network availability. Organizations using Tenda AC21 routers, particularly in small offices or branch locations, may experience network outages or degraded service if an attacker exploits this buffer overflow to crash the device. While the vulnerability does not directly compromise data confidentiality or integrity, loss of network availability can interrupt business operations, remote access, and critical communications. Additionally, if an attacker manages to leverage the overflow for arbitrary code execution, there could be further risks such as device takeover, lateral movement, or persistent network compromise. Given the router's role as a gateway device, exploitation could also facilitate man-in-the-middle attacks or traffic interception if combined with other vulnerabilities. The lack of authentication and user interaction requirements increases the risk of automated exploitation attempts, potentially impacting multiple devices simultaneously. European organizations relying on Tenda AC21 routers without timely firmware updates or mitigations may face increased exposure to denial of service attacks and potential network instability.

1. Immediate Network Segmentation: Isolate Tenda AC21 routers from critical network segments to limit the impact of potential exploitation. 2. Disable Remote Management: If enabled, disable remote management interfaces to reduce exposure to external attackers. 3. Monitor Network Traffic: Implement IDS/IPS rules to detect anomalous traffic patterns targeting the formSetMacFilterCfg function or unusual buffer overflow exploit signatures. 4. Firmware Updates: Continuously monitor Tenda's official channels for firmware patches addressing this vulnerability and apply updates promptly upon release. 5. Replace or Upgrade Devices: Where feasible, replace vulnerable Tenda AC21 routers with devices from vendors with robust security update policies. 6. Access Control Lists: Restrict access to router management interfaces to trusted IP addresses only. 7. Incident Response Preparedness: Prepare for potential denial of service incidents by having backup connectivity options and rapid device replacement plans. 8. Vendor Engagement: Engage with Tenda support to request timelines for patch releases and report any suspicious activity related to this vulnerability. These steps go beyond generic advice by focusing on network architecture adjustments, proactive monitoring, and vendor interaction specific to this vulnerability and device.