CVE-2025-20737 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 operation on the stack. This memory corruption can be exploited by a local attacker with user-level execution privileges to escalate their privileges to a higher level, potentially gaining kernel-level code execution. The vulnerability does not require user interaction, increasing its risk profile. Affected versions include SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02, which are commonly used in embedded wireless devices and routers. The CVSS v3.1 base score is 7.8, indicating high severity, with attack vector local, low attack complexity, privileges required at user level, no user interaction, and high impact on confidentiality, integrity, and availability. Although no exploits have been reported in the wild yet, the vulnerability’s nature makes it a critical concern for devices that rely on these MediaTek chipsets for wireless connectivity. The issue is tracked internally by MediaTek as MSV-4040 and patch ID WCNCR00435343, though no public patch links are currently provided.

For European organizations, this vulnerability poses a significant risk to the security of wireless infrastructure devices such as routers, access points, and embedded systems that incorporate the affected MediaTek chipsets. Successful exploitation could allow attackers to escalate privileges locally, potentially leading to full device compromise. This could result in unauthorized access to sensitive network traffic, disruption of wireless services, and the ability to pivot within internal networks. Critical sectors such as telecommunications, finance, government, and industrial control systems that rely on these devices could face confidentiality breaches, service outages, and integrity violations. The lack of required user interaction and the relatively low complexity of exploitation increase the likelihood of attacks, especially in environments where local access or compromised user accounts exist. The vulnerability could also be leveraged in supply chain attacks or by insiders to undermine network security.

European organizations should immediately inventory their network devices and embedded systems to identify those using the affected MediaTek chipsets and firmware versions. Until official patches are released, organizations should restrict local access to these devices, enforce strict user privilege management, and monitor for unusual local activity indicative of exploitation attempts. Network segmentation should be employed to limit the impact of a compromised device. Where possible, upgrade to newer firmware versions beyond SDK 7.6.7.2 and openWRT 21.02 once patches are available. Employ host-based intrusion detection systems (HIDS) and endpoint protection to detect anomalous behavior related to privilege escalation. Vendors and integrators should be contacted to obtain timely security updates. Additionally, disabling unnecessary services and interfaces on affected devices can reduce the attack surface. Regular security audits and penetration testing focusing on wireless infrastructure will help identify exploitation attempts early.