CVE-2025-20686 is a heap overflow vulnerability identified in the WLAN Access Point (AP) driver of several MediaTek chipsets, specifically MT6890, MT7915, MT7916, MT7981, and MT7986. The root cause is an incorrect bounds check in the driver code, which leads to an out-of-bounds write on the heap. This type of vulnerability is classified under CWE-122 (Heap-based Buffer Overflow). Exploitation of this flaw can allow an attacker in close proximity—such as within wireless range—to execute arbitrary code remotely on the affected device without requiring any additional privileges or user interaction. The vulnerability affects SDK release 7.6.7.2 and earlier versions, as well as OpenWrt versions 19.07 and 21.02 for the MT6890 chipset. The lack of need for user interaction and the ability to execute code remotely make this a particularly dangerous vulnerability. Although no known exploits are currently reported in the wild, the potential for remote code execution via wireless proximity makes this a critical security concern for devices using these MediaTek chipsets, which are commonly embedded in wireless routers, IoT devices, and other network infrastructure components. The vulnerability was publicly disclosed on July 8, 2025, and is tracked under the internal issue ID MSV-3404 and patch ID WCNCR00415570, although no public patch links are currently available. Given the nature of the vulnerability, successful exploitation could lead to full compromise of the affected device, enabling attackers to manipulate network traffic, pivot into internal networks, or disrupt device availability.

For European organizations, this vulnerability poses significant risks, especially for enterprises and service providers relying on wireless infrastructure equipped with the affected MediaTek chipsets. Compromise of wireless access points or routers could lead to unauthorized access to internal networks, data exfiltration, or disruption of critical services. The proximity-based attack vector means attackers could exploit this vulnerability from nearby locations such as public spaces, parking lots, or adjacent offices, increasing the attack surface in urban and densely populated areas. This is particularly concerning for sectors with high security requirements, such as government, finance, healthcare, and critical infrastructure. Additionally, many IoT devices and consumer-grade routers in European markets use MediaTek chipsets, potentially exposing small and medium enterprises and residential users to risks that could cascade into broader network compromises. The absence of user interaction requirements and the ability to execute code remotely elevate the threat level, potentially enabling attackers to establish persistent footholds or launch further attacks within organizational networks.

To mitigate this vulnerability effectively, European organizations should: 1) Identify and inventory all devices using the affected MediaTek chipsets, including routers, access points, and IoT devices, by leveraging network asset management tools and vendor documentation. 2) Monitor vendor communications closely for official patches or firmware updates addressing CVE-2025-20686 and apply them promptly once available. 3) In the absence of immediate patches, implement network segmentation to isolate vulnerable wireless devices from critical internal systems, reducing potential lateral movement. 4) Employ wireless intrusion detection and prevention systems (WIDS/WIPS) to detect anomalous wireless activity that could indicate exploitation attempts. 5) Restrict physical access and proximity to wireless infrastructure where feasible, and consider deploying directional antennas or reducing wireless signal strength to limit exposure. 6) For organizations using OpenWrt-based devices, upgrade to versions beyond 21.02 or apply vendor-provided patches as soon as they are released. 7) Conduct regular security assessments and penetration tests focusing on wireless infrastructure to identify and remediate potential exploitation paths. 8) Educate IT and security teams about the specific risks of proximity-based wireless attacks to enhance monitoring and incident response readiness.