CVE-2025-20720 is a heap overflow vulnerability categorized under CWE-122 found in the WLAN AP driver of several MediaTek chipsets (MT6890, MT7603, MT7615, MT7622, 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 remotely by an attacker positioned within wireless range (proximal or adjacent) without requiring any user interaction or prior authentication. The vulnerability enables escalation of privilege, potentially allowing attackers to execute arbitrary code or cause denial of service by corrupting memory structures. Affected versions include SDK release 7.6.7.2 and earlier, as well as OpenWrt 19.07 and 21.02 builds incorporating these chipsets. The vulnerability has been assigned a CVSS v3.1 base score of 8.8, indicating high severity with attack vector as adjacent network, low attack complexity, no privileges required, and no user interaction needed. While no public exploits have been reported yet, the vulnerability poses a significant risk due to the widespread use of MediaTek chipsets in consumer and enterprise wireless access points. The issue is tracked internally by MediaTek under MSV-3569 and patch ID WCNCR00418954, though no public patch links are currently available.

The impact of CVE-2025-20720 is substantial for organizations relying on wireless infrastructure powered by affected MediaTek chipsets. Successful exploitation can lead to full compromise of the wireless access point, allowing attackers to escalate privileges and potentially execute arbitrary code or disrupt network availability. This threatens the confidentiality and integrity of network traffic and connected devices, potentially enabling lateral movement within corporate networks. Given the vulnerability requires no authentication or user interaction, attackers within wireless range can exploit it stealthily, increasing risk in environments with dense wireless deployments such as enterprises, public Wi-Fi hotspots, and critical infrastructure facilities. The widespread deployment of MediaTek chipsets in consumer routers and IoT gateways further broadens the attack surface, potentially impacting home users and small businesses. The lack of known exploits currently provides a window for proactive mitigation, but the high CVSS score underscores the urgency for patching and network defense enhancements.

Organizations should immediately inventory devices using affected MediaTek chipsets and verify firmware versions against the vulnerable releases (SDK 7.6.7.2 and earlier, OpenWrt 19.07 and 21.02). Although no official patches are publicly linked yet, monitoring MediaTek advisories and vendor firmware updates is critical to apply fixes promptly once available. In the interim, network administrators should implement wireless network segmentation to isolate vulnerable access points from sensitive internal resources. Enforce strong wireless encryption and authentication to reduce unauthorized access risk. Deploy intrusion detection and prevention systems (IDS/IPS) with signatures or anomaly detection tuned for heap overflow attempts or unusual WLAN driver behavior. Limit physical proximity access to wireless networks by controlling access points’ transmit power and using directional antennas where feasible. Regularly audit and update device firmware to the latest stable versions. Additionally, consider deploying network access control (NAC) solutions to restrict device connectivity based on security posture. For environments using OpenWrt, upgrading to versions beyond 21.02 that include patches for this vulnerability is advisable once available.