CVE-2025-20742 is a heap overflow vulnerability classified under CWE-122, affecting the WLAN AP driver in multiple MediaTek chipsets (MT6890, MT7603, MT7615, MT7622, MT7915, MT7916, MT7981, MT7986). The root cause is an incorrect bounds check in the driver code, which leads to an out-of-bounds write on the heap. This memory corruption flaw can be triggered remotely by an attacker located in physical proximity or adjacent network range, without requiring any user interaction or additional execution privileges. Exploitation of this vulnerability enables escalation of privileges on the affected device, potentially allowing the attacker to execute arbitrary code or disrupt device operation. The affected software versions include SDK release 7.6.7.2 and earlier, as well as OpenWrt 19.07 and 21.02 for the MT6890 chipset. No public exploits have been reported yet, but the vulnerability's nature and ease of exploitation make it a critical concern. The issue was reserved in November 2024 and published in November 2025, with MediaTek assigning the identifier MSV-3949 and patch ID WCNCR00432680. The vulnerability impacts embedded wireless devices such as routers, access points, and IoT devices that incorporate these MediaTek chipsets, which are widely used in consumer and enterprise networking equipment. The heap overflow can compromise confidentiality, integrity, and availability by enabling attackers to gain elevated privileges and potentially control the device firmware or network traffic.

For European organizations, this vulnerability poses a significant risk to network infrastructure security, particularly for enterprises, service providers, and critical infrastructure relying on MediaTek-based wireless access points and embedded devices. Successful exploitation could allow attackers to escalate privileges remotely, leading to unauthorized access, data interception, or disruption of network services. This could impact confidentiality by exposing sensitive communications, integrity by allowing manipulation of network traffic or device settings, and availability by causing device crashes or denial of service. The lack of required user interaction and the remote nature of the attack increase the threat level, especially in environments with dense wireless deployments or public access points. Organizations in sectors such as telecommunications, finance, healthcare, and government are particularly vulnerable due to the critical nature of their network operations. Additionally, the widespread use of OpenWrt firmware in European networking devices amplifies the potential attack surface. The vulnerability could also facilitate lateral movement within networks, enabling attackers to compromise additional systems once initial access is gained.

1. Apply firmware updates and patches from MediaTek or device vendors as soon as they become available, specifically targeting SDK releases and OpenWrt versions identified as vulnerable. 2. For devices where patches are not yet available, implement network segmentation to isolate vulnerable wireless access points from critical network segments. 3. Restrict physical and wireless proximity access to sensitive devices by enforcing strong physical security controls and limiting wireless signal range where feasible. 4. Monitor network traffic for unusual activity or signs of exploitation attempts, focusing on wireless management frames and driver-level anomalies. 5. Employ intrusion detection and prevention systems capable of detecting exploitation patterns related to heap overflows and privilege escalation attempts. 6. Maintain an inventory of devices using affected MediaTek chipsets to prioritize remediation efforts. 7. Collaborate with vendors and security communities to stay informed about patch releases and emerging exploit techniques. 8. Consider deploying endpoint protection solutions that can detect and block privilege escalation attempts on embedded devices. 9. Conduct regular security audits and penetration testing focused on wireless infrastructure to identify residual risks. 10. Educate network administrators about the vulnerability and the importance of timely patching and monitoring.