CVE-2025-20734 is a heap overflow vulnerability identified 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 that leads to an out-of-bounds write operation on the heap memory. This vulnerability falls under CWE-122 (Heap-based Buffer Overflow). The flaw allows a local attacker who already possesses System-level privileges to escalate their privileges further, potentially gaining higher control over the device or executing arbitrary code in kernel mode. Notably, exploitation does not require any user interaction, increasing the risk if an attacker gains initial system access. The 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 such as routers and IoT gateways. Although no public exploits have been reported, the vulnerability's presence in widely deployed chipsets used in network infrastructure devices makes it a significant concern. The vulnerability was published on November 4, 2025, with no CVSS score assigned yet. The issue is tracked internally by MediaTek as MSV-4112 and patch ID WCNCR00441507. Due to the nature of the vulnerability, attackers must have local system access with elevated privileges to exploit it, limiting remote exploitation but increasing the risk of persistent local attacks or insider threats. The heap overflow can lead to memory corruption, potentially causing system crashes or arbitrary code execution, undermining device integrity and availability.

For European organizations, the impact of CVE-2025-20734 can be significant, especially for those relying on network infrastructure devices and IoT equipment powered by affected MediaTek chipsets. Successful exploitation could allow attackers with local system access to escalate privileges, potentially gaining full control over routers, wireless access points, or IoT gateways. This could lead to unauthorized configuration changes, interception or manipulation of network traffic, installation of persistent malware, or denial of service conditions. Critical sectors such as telecommunications, manufacturing, healthcare, and smart city infrastructure that deploy embedded wireless devices are at heightened risk. The vulnerability could facilitate lateral movement within networks if attackers leverage compromised devices as footholds. Additionally, the lack of user interaction requirement means that once local access is obtained, exploitation can be automated or triggered remotely by malware already running on the device. The absence of known public exploits currently reduces immediate risk, but the widespread use of MediaTek chipsets in consumer and enterprise devices means that the threat landscape could evolve rapidly once exploit code becomes available.

1. Monitor MediaTek and openWRT vendor advisories closely for official patches addressing CVE-2025-20734 and apply them promptly to all affected devices. 2. Restrict local system access to trusted administrators only, employing strong authentication and access controls to reduce the risk of attackers gaining initial System privileges. 3. Implement network segmentation to isolate critical wireless infrastructure devices from general user networks, limiting the impact of any local compromise. 4. Employ host-based intrusion detection systems (HIDS) and endpoint protection solutions capable of detecting anomalous behavior indicative of privilege escalation attempts. 5. Regularly audit device firmware versions and configurations to identify and remediate outdated or vulnerable deployments. 6. For openWRT users, consider upgrading to versions beyond 21.02 once patches are integrated or apply community patches if available. 7. Use secure boot and firmware integrity verification mechanisms where supported to prevent unauthorized firmware modifications. 8. Educate system administrators about the risks of local privilege escalation vulnerabilities and the importance of minimizing privileged access.