CVE-2025-20733 is a heap overflow vulnerability classified under CWE-122, 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 allows an out-of-bounds write to heap memory. This flaw can be exploited locally by an attacker with user-level execution privileges to escalate their privileges on the device, potentially gaining kernel-level or administrative control. The vulnerability does not require user interaction, making it easier to exploit once local access is obtained. Affected software versions include MediaTek 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 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects that the attack requires local access but has low complexity, no user interaction, and impacts confidentiality, integrity, and availability at a high level. Although no public exploits have been reported, the vulnerability poses a serious risk to devices running these drivers, potentially allowing attackers to compromise network infrastructure components. The issue is tracked under MediaTek’s internal ID MSV-4138 and patch ID WCNCR00441509, but no public patch links are currently provided.

For European organizations, this vulnerability threatens the security of wireless networking infrastructure that relies on MediaTek chipsets, including enterprise access points, routers, and embedded IoT devices. Successful exploitation could allow attackers to escalate privileges locally, potentially leading to full device compromise, unauthorized access to sensitive network traffic, and disruption of network availability. This could impact confidentiality by exposing internal communications, integrity by allowing malicious modifications to device firmware or configurations, and availability by causing device crashes or denial of service. Given the widespread use of openWRT in European networking devices and the presence of MediaTek hardware in consumer and enterprise equipment, the vulnerability could affect a broad range of sectors including telecommunications, critical infrastructure, and enterprises. The lack of required user interaction and low attack complexity increases the risk of exploitation in environments where local access is possible, such as shared office spaces or compromised internal networks.

European organizations should immediately identify devices using the affected MediaTek chipsets and firmware versions (SDK 7.6.7.2 and earlier, openWRT 19.07 and 21.02). They should prioritize upgrading to patched firmware versions once available from device vendors or MediaTek. In the interim, restrict local access to networking devices by enforcing strict physical security controls and network segmentation to limit exposure to untrusted users. Employ host-based intrusion detection systems to monitor for anomalous behavior indicative of privilege escalation attempts. Regularly audit device configurations and firmware versions to ensure compliance with security policies. Collaborate with vendors to obtain timely patches and verify their deployment. Additionally, consider deploying network-level protections such as access control lists and network segmentation to reduce the risk of lateral movement by attackers who gain local access. Finally, maintain up-to-date asset inventories to quickly identify and remediate vulnerable devices.