CVE-2025-20729 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 vulnerability can be exploited locally by an attacker who already possesses System-level privileges on the device, enabling them to escalate their privileges further, potentially gaining higher control or bypassing security mechanisms. Exploitation does not require user interaction, increasing the risk if 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. The CVSS v3.1 base score is 4.2, reflecting a medium severity due to the requirement of high privileges for exploitation and limited impact scope. No public exploits have been reported yet, but the vulnerability poses a risk to the confidentiality, integrity, and availability of systems using these chipsets, especially in embedded networking devices such as routers and access points. The issue has been assigned patch ID WCNCR00441512 and issue ID MSV-4153 by MediaTek, indicating that a fix is or will be available.

For European organizations, this vulnerability could lead to unauthorized privilege escalation on devices using affected MediaTek chipsets, primarily embedded in wireless access points and routers. This could compromise network infrastructure integrity, allowing attackers to manipulate network traffic, disrupt services, or gain deeper access to internal networks. Confidentiality of sensitive data transmitted over affected devices could be at risk if attackers leverage escalated privileges to intercept or modify communications. Availability could also be impacted if attackers cause device crashes or instability through exploitation. Organizations relying on openWRT-based devices or SDK releases with these chipsets are particularly vulnerable. The medium severity score reflects that exploitation requires existing high privileges, limiting the threat to scenarios where attackers have already penetrated the system. However, given the widespread use of MediaTek chipsets in consumer and enterprise networking equipment across Europe, the potential for lateral movement and further compromise within networks is significant if unpatched.

European organizations should immediately inventory their networking devices to identify those using the affected MediaTek chipsets and software versions. Prioritize updating to patched SDK releases or openWRT versions once MediaTek releases the fix corresponding to patch ID WCNCR00441512. Until patches are applied, restrict local administrative access to affected devices to trusted personnel only and monitor for unusual activities indicating privilege escalation attempts. Employ network segmentation to limit the impact of compromised devices and use endpoint detection and response (EDR) tools to detect anomalous behavior on devices with these chipsets. Additionally, consider deploying network intrusion detection systems (NIDS) to monitor for suspicious traffic patterns that may indicate exploitation attempts. Regularly review and harden device configurations to minimize attack surface, including disabling unnecessary services and enforcing strong authentication methods. Engage with vendors and suppliers to ensure timely updates and verify that firmware and software are up to date.