CVE-2025-20685 is a heap overflow vulnerability identified in the WLAN Access Point (AP) driver of several MediaTek chipsets, specifically the MT6890, MT7915, MT7916, MT7981, and MT7986 models. The root cause is an incorrect bounds check in the driver code, which allows an out-of-bounds write operation on the heap. This type of vulnerability is classified under CWE-122 (Heap-based Buffer Overflow). Exploitation of this flaw can lead to remote code execution by an attacker located in proximity or adjacent to the vulnerable device, such as within wireless range, without requiring any additional execution privileges or user interaction. The vulnerability affects SDK releases up to 7.6.7.2 and OpenWrt versions 19.07 and 21.02 for the MT6890 chipset. Although no public exploits have been reported in the wild yet, the nature of the vulnerability—heap overflow in a wireless driver—makes it a critical concern because it can be triggered remotely and silently. The lack of a CVSS score suggests that the vulnerability is newly published and pending formal severity assessment, but the technical details indicate a high-risk scenario due to the potential for remote code execution without user interaction or authentication. The issue has been tracked internally by MediaTek under Issue ID MSV-3409 and Patch ID WCNCR00416226, but no public patch links are currently available.

For European organizations, this vulnerability poses a significant risk, especially for those relying on wireless infrastructure powered by MediaTek chipsets in their networking equipment or IoT devices. Successful exploitation could allow attackers to execute arbitrary code remotely, potentially leading to full compromise of affected devices. This could result in unauthorized access to internal networks, data exfiltration, lateral movement within corporate environments, or disruption of critical wireless services. Given the proximity-based attack vector, attackers could operate from nearby physical locations such as public spaces, office perimeters, or even adjacent buildings, making it difficult to detect or prevent without proper wireless security controls. The impact is particularly severe for sectors with high reliance on wireless connectivity, including telecommunications, manufacturing, healthcare, and smart city infrastructure. Additionally, the absence of user interaction requirements increases the risk of automated or stealthy attacks. The vulnerability could also be leveraged in targeted attacks against European entities, especially those with strategic or sensitive operations, amplifying geopolitical risks.

European organizations should prioritize the following mitigation steps: 1) Inventory and identify all devices using the affected MediaTek chipsets, including embedded systems, wireless access points, and IoT devices. 2) Monitor vendor communications closely for official patches or firmware updates addressing CVE-2025-20685 and apply them promptly once available. 3) Until patches are deployed, implement network segmentation to isolate vulnerable wireless devices from critical internal networks and sensitive data repositories. 4) Enhance wireless network security by enforcing strong encryption (WPA3 where possible), disabling unnecessary wireless services, and restricting wireless access to trusted devices only. 5) Deploy wireless intrusion detection and prevention systems (WIDS/WIPS) to detect anomalous or suspicious wireless activity indicative of exploitation attempts. 6) Conduct regular security assessments and penetration tests focusing on wireless infrastructure to identify potential exploitation vectors. 7) Educate security teams about the proximity-based nature of this threat to increase vigilance around physical security and wireless perimeter monitoring. 8) Consider temporary disabling or restricting use of vulnerable devices in high-risk environments until patches are available. These steps go beyond generic advice by focusing on device identification, network architecture adjustments, and enhanced wireless security controls tailored to the nature of this vulnerability.