CVE-2025-20715 is a vulnerability classified under CWE-787 (Out-of-bounds Write) found in the WLAN AP driver of multiple MediaTek chipsets: 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 condition. This flaw can be exploited by a local attacker who already has System-level privileges on the device, enabling them to escalate their privileges further, potentially gaining higher control or bypassing security mechanisms. The vulnerability does not require user interaction, making it easier to exploit once initial access is obtained. Affected versions include SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02 for the MT6890 chipset. The vulnerability impacts confidentiality, integrity, and availability, as an attacker could manipulate memory to execute arbitrary code or cause denial of service. The CVSS v3.1 base score is 7.8, reflecting high severity with attack vector local, low attack complexity, low privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. No public exploits have been reported yet, but the issue is recognized and patches are expected. The vulnerability is tracked under MediaTek's internal issue MSV-3731 and patch ID WCNCR00421152.

The vulnerability allows a local attacker with existing System privileges to perform an out-of-bounds write, which can lead to privilege escalation. This can compromise the confidentiality, integrity, and availability of the affected device. In practical terms, an attacker could execute arbitrary code with elevated privileges, potentially gaining full control over the device, modifying firmware, or disrupting wireless communications. This is particularly critical for devices acting as wireless access points or embedded systems in enterprise or industrial environments. The impact extends to any organization deploying affected MediaTek chipsets in their networking infrastructure, IoT devices, or embedded systems, risking data breaches, service outages, or further lateral movement within networks. Since no user interaction is required, the vulnerability can be exploited stealthily once initial access is obtained. Although exploitation requires prior system-level access, the escalation potential makes it a significant threat in multi-tenant or shared environments where privilege boundaries are critical.

Organizations should immediately inventory devices using the affected MediaTek chipsets and verify firmware and SDK versions. Apply patches or firmware updates from MediaTek or device vendors as soon as they become available, specifically targeting SDK releases newer than 7.6.7.2 and openWRT versions beyond 21.02 for MT6890. Until patches are deployed, restrict local access to trusted users only and implement strict access controls to prevent unauthorized system-level access. Employ runtime protections such as memory protection mechanisms (e.g., DEP, ASLR) where supported by the device to mitigate exploitation impact. Monitor logs and system behavior for signs of privilege escalation attempts. Network segmentation can limit the impact of compromised devices. Engage with vendors for timely updates and validate patch integrity before deployment. For custom or embedded systems, review and harden WLAN AP driver configurations and consider disabling unnecessary wireless features if feasible. Regularly update and audit device firmware to reduce exposure to similar vulnerabilities.