CVE-2025-20734 is a heap overflow vulnerability classified under CWE-122 found in the WLAN Access Point (AP) driver of several 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 allows an out-of-bounds write to heap memory. 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 or bypassing security restrictions. The vulnerability does not require user interaction, making it easier to exploit once the attacker has local system access. The affected software 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 devices and wireless routers. The CVSS v3.1 base score is 5.3, reflecting a medium severity level, with attack vector being local, low attack complexity, requiring low privileges, and no user interaction. The impact includes limited confidentiality, integrity, and availability loss due to the prerequisite of system privileges. No public exploits or patches are currently available, but the issue has been officially published and tracked by MediaTek under issue ID MSV-4112 and patch ID WCNCR00441507. This vulnerability is significant for organizations relying on MediaTek wireless chipsets in their network infrastructure, as it could be leveraged for lateral movement or persistence by attackers with initial system access.

For European organizations, the primary impact of CVE-2025-20734 lies in the potential for local privilege escalation on devices using affected MediaTek chipsets, which are prevalent in embedded wireless access points and routers. While initial exploitation requires system-level access, successful exploitation could allow attackers to gain deeper control over network devices, potentially leading to unauthorized configuration changes, interception or manipulation of network traffic, and disruption of wireless services. This could affect confidentiality by exposing sensitive network data, integrity by allowing unauthorized modifications, and availability by destabilizing network infrastructure. Critical sectors such as telecommunications, government, finance, and industrial control systems that rely on embedded wireless devices are particularly at risk. The vulnerability could also facilitate lateral movement within internal networks, increasing the attack surface. Given the widespread use of openWRT in European networking equipment, organizations using affected versions should be vigilant. The absence of known exploits in the wild currently reduces immediate risk, but the medium severity and ease of exploitation once system access is obtained warrant proactive mitigation.

European organizations should implement the following specific mitigations: 1) Inventory all network devices and embedded systems to identify those using affected MediaTek chipsets and SDK/openWRT versions. 2) Monitor vendor communications closely for official patches or firmware updates addressing CVE-2025-20734 and apply them promptly once available. 3) Restrict local system access to trusted administrators only, employing strong authentication and access controls to prevent unauthorized privilege acquisition. 4) Employ network segmentation to limit the ability of an attacker with system access on one device to move laterally to others. 5) Use host-based intrusion detection systems (HIDS) and endpoint protection to detect anomalous behavior indicative of privilege escalation attempts. 6) Regularly audit and harden device configurations, disabling unnecessary services and interfaces that could be leveraged for local attacks. 7) For openWRT users, consider upgrading to versions beyond 21.02 or applying community patches if official fixes are delayed. 8) Conduct penetration testing and vulnerability assessments focusing on wireless infrastructure to identify potential exploitation paths. 9) Educate IT staff about the risks of local privilege escalation vulnerabilities and the importance of timely patching. 10) Implement logging and monitoring of system-level events on affected devices to enable rapid detection and response to suspicious activities.