CVE-2025-20714 is a stack overflow vulnerability classified under CWE-121 found in the WLAN Access Point (AP) driver of several MediaTek chipsets (MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, MT7986). The root cause is an incorrect bounds check in the driver code that leads to an out-of-bounds write on the stack. This memory corruption can be exploited by a local attacker who already possesses System-level privileges to escalate their privileges further, potentially gaining higher-level control over the device or system. The vulnerability does not require user interaction, which increases the risk of automated exploitation once an attacker has initial access. The affected software versions include SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02 for the MT6890 chipset. The CVSS v3.1 score of 7.8 reflects high severity due to the combination of local attack vector, low attack complexity, required privileges, and impact on confidentiality, integrity, and availability. Although no public exploits are known at this time, the vulnerability poses a significant risk to devices using these MediaTek chipsets, especially in embedded wireless infrastructure. The issue has been assigned Patch ID WCNCR00432659 and Issue ID MSV-3902 by MediaTek, but no public patch links are currently available.

For European organizations, this vulnerability could lead to unauthorized privilege escalation on devices using affected MediaTek chipsets in their wireless access points or embedded systems. This could compromise the confidentiality of sensitive data transmitted over wireless networks, integrity of device firmware or configurations, and availability of network services if exploited to disrupt operations. Organizations relying on embedded wireless infrastructure in critical sectors such as telecommunications, manufacturing, or public services may face operational disruptions or data breaches. Since exploitation requires prior System-level access, the vulnerability could be leveraged as a secondary attack vector following initial compromise, increasing the attacker's control and persistence. The broad range of affected chipsets and inclusion in popular open-source firmware like openWRT increases the potential attack surface across various device manufacturers and network environments in Europe.

European organizations should immediately inventory their wireless infrastructure and embedded devices to identify those using the affected MediaTek chipsets and firmware versions. Apply vendor-supplied patches or firmware updates as soon as they become available, referencing MediaTek's Patch ID WCNCR00432659 and Issue ID MSV-3902. Where patches are not yet available, consider temporary mitigations such as restricting local administrative access to trusted personnel only, implementing strict network segmentation to limit exposure of vulnerable devices, and monitoring for unusual privilege escalation attempts or anomalous system behavior. Employ host-based intrusion detection systems (HIDS) to detect exploitation attempts targeting the WLAN AP driver. Additionally, review and harden device configurations to minimize the attack surface, disable unnecessary services, and enforce strong authentication controls to prevent initial System-level compromise. Collaborate with device vendors and firmware maintainers to expedite patch deployment and verify update integrity.