CVE-2026-20408 is a heap buffer overflow vulnerability classified under CWE-122, found in several MediaTek wireless chipsets including MT6890, MT7615, MT7915, MT7916, MT7981, and MT7986. The vulnerability exists in the WLAN component of these chipsets and arises due to an out-of-bounds write on the heap, which can be triggered remotely by an attacker in close physical proximity to the device. This flaw allows the attacker to escalate privileges on the device without requiring any additional execution privileges or user interaction, making it a potent vector for compromise. The affected software versions include SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07, 21.02, and 23.05, which are commonly used in embedded wireless devices and routers. Although no public exploits have been reported yet, the nature of the vulnerability suggests that exploitation could lead to unauthorized control over the wireless device, potentially allowing attackers to manipulate network traffic, intercept sensitive data, or disrupt wireless communications. The vulnerability was reserved in November 2025 and published in February 2026, but no CVSS score has been assigned yet. The lack of required user interaction and the ability to escalate privileges remotely increase the risk profile significantly. The vulnerability affects the confidentiality, integrity, and availability of affected devices, especially in environments where wireless access points or routers using these chipsets are deployed.

For European organizations, this vulnerability could have serious consequences, particularly for enterprises and critical infrastructure relying on wireless connectivity based on MediaTek chipsets. Successful exploitation could allow attackers to gain elevated privileges on wireless devices, enabling interception or manipulation of network traffic, unauthorized access to internal networks, and disruption of wireless services. This could impact confidentiality by exposing sensitive communications, integrity by allowing malicious modifications, and availability by potentially causing device crashes or denial of service. Sectors such as telecommunications, government, healthcare, and finance that depend heavily on secure wireless communications are at heightened risk. Additionally, the proximity requirement for exploitation means that attackers need to be physically near the target, which could be feasible in public or semi-public spaces such as offices, campuses, or urban environments. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, especially as patches are not yet widely available. Organizations using openWRT-based devices or custom firmware with these chipsets are also vulnerable, broadening the scope of affected systems.

European organizations should take proactive steps to mitigate this vulnerability. First, they should inventory all wireless devices and routers using the affected MediaTek chipsets and verify firmware versions against the vulnerable SDK and openWRT releases. Immediate mitigation includes applying vendor patches or firmware updates as soon as they become available, referencing Patch ID WCNCR00461651 and Issue ID MSV-4758. Until patches are deployed, network segmentation should be enforced to isolate vulnerable wireless devices from critical internal networks. Implementing strong physical security controls to limit attacker proximity to wireless infrastructure is essential, such as securing access points in locked enclosures or restricted areas. Monitoring wireless network traffic for anomalies and unauthorized access attempts can help detect exploitation attempts early. Additionally, disabling unnecessary wireless services and reducing wireless signal range where feasible can reduce exposure. Organizations should also engage with vendors and open source communities to track patch releases and verify update integrity. Finally, incorporating this vulnerability into incident response plans will prepare teams for rapid action if exploitation is detected.