CVE-2025-20681 is a security vulnerability identified in several MediaTek wireless chipset models, specifically MT6890, MT7615, MT7622, MT7663, and MT7915. The flaw exists within the WLAN Access Point (AP) driver component, where an incorrect bounds check leads to an out-of-bounds write condition (classified under CWE-787). This type of vulnerability occurs when the software writes data outside the boundaries of allocated memory buffers, potentially corrupting adjacent memory. Exploitation of this vulnerability requires local user privileges but does not require user interaction, meaning an attacker with user-level execution rights on a device using the affected MediaTek chipsets can trigger the flaw without additional input from other users. The consequence of this out-of-bounds write is a local privilege escalation, allowing an attacker to gain higher system privileges than initially granted. This could enable unauthorized access to sensitive system functions or data, potentially compromising the device's integrity and security. Affected software versions include SDK release 5.1.0.0 and earlier, as well as openWRT versions 19.07 and 21.02 that utilize these chipsets. Although no known exploits are currently reported in the wild, the vulnerability's nature and the absence of required user interaction make it a significant risk if weaponized. No CVSS score has been assigned yet, and no official patch links are provided, but MediaTek has acknowledged the issue under Patch ID WCNCR00416936 and Issue ID MSV-3446.

For European organizations, this vulnerability poses a considerable risk, especially for those relying on network infrastructure or IoT devices powered by the affected MediaTek chipsets. The local privilege escalation could allow attackers who have gained limited access—such as through compromised user accounts or insider threats—to elevate their privileges and execute arbitrary code with higher system rights. This can lead to unauthorized configuration changes, data exfiltration, or disruption of network services. Given that openWRT is widely used in custom and embedded networking devices, including routers and gateways, the vulnerability could affect critical network infrastructure components. This may impact confidentiality, integrity, and availability of network communications within corporate environments. Additionally, the lack of required user interaction lowers the barrier for exploitation once local access is obtained, increasing the threat level. The absence of known exploits currently provides a window for mitigation, but organizations should act proactively to prevent potential attacks. The vulnerability could also affect supply chains and managed service providers using affected hardware, amplifying the impact across multiple sectors.

European organizations should prioritize the following mitigation steps: 1) Inventory and identify all devices and network equipment using MediaTek chipsets MT6890, MT7615, MT7622, MT7663, and MT7915, especially those running SDK release 5.1.0.0 or earlier and openWRT 19.07 or 21.02. 2) Engage with hardware vendors and MediaTek to obtain and apply any available patches or firmware updates addressing this vulnerability (referencing Patch ID WCNCR00416936). 3) Where patches are not yet available, implement strict access controls to limit local user privileges and restrict administrative access to trusted personnel only. 4) Monitor device logs and network traffic for unusual activity indicative of privilege escalation attempts. 5) Employ network segmentation to isolate vulnerable devices from critical infrastructure to reduce potential lateral movement. 6) Consider deploying endpoint detection and response (EDR) solutions capable of detecting anomalous behavior related to memory corruption or privilege escalation. 7) For openWRT users, evaluate upgrading to newer, supported versions beyond 21.02 that may include security fixes or consider alternative firmware with active security maintenance. 8) Educate IT staff about the vulnerability and the importance of minimizing local user access on affected devices.