CVE-2025-20748 is a vulnerability categorized under CWE-787 (Out-of-bounds Write) found in the wlan AP driver of multiple MediaTek chipsets including MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986. The root cause is an incorrect bounds check in the driver code, which leads to a write operation outside the allocated memory boundaries. This memory corruption can be exploited by a local attacker who already possesses System-level privileges to escalate their privileges further, potentially gaining higher control over the device or system. The vulnerability does not require user interaction, which simplifies exploitation once the attacker has initial access. Affected software includes MediaTek SDK release 7.6.7.2 and earlier versions, as well as openWRT versions 19.07 and 21.02 that incorporate these drivers. The vulnerability impacts confidentiality, integrity, and availability, as arbitrary memory writes can lead to code execution or system instability. Although no exploits have been observed in the wild, the presence of this vulnerability in widely deployed wireless access point chipsets and embedded devices poses a significant risk. The CVSS v3.1 base score of 6.7 reflects a medium severity with local attack vector, low attack complexity, high privileges required, no user interaction, and impacts across all three security properties. The issue is tracked under MediaTek’s internal ID MSV-3950 and patch ID WCNCR00432679, though no public patch links are currently provided.

For European organizations, this vulnerability could lead to local privilege escalation on devices using affected MediaTek chipsets, such as wireless access points, routers, and embedded IoT devices. This could allow attackers who have already compromised a system with System privileges to gain full control, potentially leading to unauthorized configuration changes, interception or manipulation of network traffic, or persistent backdoors. Critical infrastructure, enterprise networks, and service providers relying on MediaTek-based networking hardware could face increased risk of lateral movement and deeper compromise. The impact is heightened in environments where these devices are used for sensitive communications or as part of security perimeter controls. Additionally, the vulnerability could affect managed service providers and telecom operators using openWRT-based devices, which are common in Europe. The lack of user interaction requirement means that once initial access is gained, exploitation can be automated, increasing the threat level. Although no known exploits exist yet, the medium severity and broad impact on confidentiality, integrity, and availability warrant proactive mitigation.

Organizations should immediately inventory devices using MediaTek chipsets MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986, particularly those running SDK release 7.6.7.2 or earlier and openWRT versions 19.07 or 21.02. Apply vendor-supplied patches or firmware updates as soon as they become available from MediaTek or device manufacturers. If patches are not yet available, consider isolating affected devices on segmented networks to limit potential lateral movement. Employ strict access controls to prevent unauthorized local access, as exploitation requires System privileges. Monitor logs and network traffic for unusual activity indicative of privilege escalation attempts. For openWRT deployments, upgrade to the latest stable releases that may include fixes or mitigations. Engage with vendors and suppliers to confirm patch availability and timelines. Additionally, implement endpoint detection and response (EDR) solutions capable of detecting anomalous memory corruption or privilege escalation behaviors on affected devices. Regularly review and harden device configurations to minimize attack surface.