CVE-2025-20736 is a stack overflow vulnerability classified under CWE-121 found in the wlan 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 leads to an out-of-bounds write on the stack. This memory corruption flaw can be exploited locally by an attacker who already possesses System-level privileges on the device, enabling them to escalate privileges further or execute arbitrary code with elevated rights. The vulnerability does not require any user interaction, increasing its risk in environments where local access is possible. The affected software versions include SDK release 7.6.7.2 and earlier, as well as openWRT releases 19.07 and 21.02, which are commonly used in embedded devices and routers. Although no public exploits have been reported, the vulnerability's nature suggests that exploitation could lead to system compromise or denial of service. The issue was reserved in November 2024 and published in November 2025, with MediaTek identified as the assigner. No CVSS score has been assigned yet, and no patch links are currently provided, indicating that remediation may still be in progress or pending deployment. The vulnerability is significant for devices relying on these chipsets for wireless access point functionality, including enterprise networking equipment and consumer IoT devices.

For European organizations, this vulnerability poses a risk primarily to local network infrastructure and embedded devices using affected MediaTek chipsets. Since exploitation requires existing System privileges, the threat is elevated in environments where insider threats or compromised local accounts exist. Successful exploitation could lead to privilege escalation, allowing attackers to gain full control over affected devices, potentially disrupting network availability or enabling lateral movement within internal networks. This could impact confidentiality and integrity of data traversing or managed by these devices. Given the widespread use of MediaTek chipsets in routers, access points, and IoT devices, critical infrastructure sectors such as telecommunications, manufacturing, and smart city deployments could be affected. The lack of user interaction requirement increases the risk in automated or unattended systems. The absence of known exploits suggests a window for proactive mitigation, but organizations should act swiftly to prevent potential future attacks. Failure to address this vulnerability could result in operational disruptions, data breaches, or compromised network security posture.

1. Monitor MediaTek and openWRT vendor channels closely for official patches or firmware updates addressing CVE-2025-20736 and apply them immediately upon release. 2. Restrict local access to devices running affected chipsets to trusted personnel only, minimizing the risk of privilege escalation by malicious insiders or compromised accounts. 3. Implement strict access controls and network segmentation to limit the impact of any compromised device within the network. 4. Employ host-based intrusion detection systems (HIDS) and endpoint monitoring to detect unusual privilege escalation attempts or anomalous behavior on devices with these chipsets. 5. For openWRT users, consider upgrading to versions beyond 21.02 once patches are available or apply community-recommended mitigations if official patches are delayed. 6. Conduct regular security audits and vulnerability assessments focusing on embedded devices and wireless infrastructure to identify and remediate similar issues proactively. 7. Educate system administrators and security teams about the vulnerability specifics to enhance detection and response capabilities. 8. Where feasible, replace legacy devices running vulnerable firmware with updated hardware supporting secure and patched software stacks.