CVE-2025-20716 is an out-of-bounds write vulnerability classified under CWE-787, found in the WLAN Access Point (AP) driver of multiple 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 allows writing outside the intended memory buffer. This memory corruption can be exploited by a local attacker who already has system-level privileges to escalate their privileges further, potentially gaining unrestricted control over the affected device. The vulnerability does not require any user interaction, increasing the risk of automated or stealthy exploitation. 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 CVSS v3.1 base score is 7.8, reflecting high severity with high impact on confidentiality, integrity, and availability, and requiring low attack complexity but needing some privileges. Although no public exploits have been reported yet, the vulnerability poses a significant risk to embedded systems and network devices using these chipsets, especially in environments where attackers can gain initial system access. The issue has been assigned patch ID WCNCR00421149 and issue ID MSV-3728 by MediaTek, but no public patch links are currently available.

For European organizations, this vulnerability poses a serious threat to the security of network infrastructure devices such as routers, access points, and IoT devices that incorporate the affected MediaTek chipsets. Successful exploitation could allow attackers to escalate privileges locally, potentially leading to full device compromise, unauthorized data access, or disruption of network services. This is particularly critical for enterprises and service providers relying on embedded devices running openWRT or SDK versions affected by this flaw. The confidentiality, integrity, and availability of network communications and connected systems could be severely impacted. Additionally, critical infrastructure sectors using these devices may face increased risk of targeted attacks or lateral movement within networks. The lack of required user interaction and relatively low attack complexity further increase the threat level. Although no exploits are currently known in the wild, the vulnerability could be weaponized by advanced persistent threat actors or malware to deepen footholds in compromised environments.

European organizations should prioritize identifying and inventorying devices using the affected MediaTek chipsets and firmware versions, including embedded routers and IoT devices running openWRT 19.07, 21.02, or SDK releases 7.6.7.2 and earlier. Immediate mitigation involves applying vendor-supplied patches once available; organizations should engage with MediaTek or device manufacturers to obtain and deploy updates promptly. In the interim, restrict local access to affected devices by enforcing strict access controls, network segmentation, and monitoring for unusual privilege escalation attempts. Employ host-based intrusion detection systems (HIDS) and endpoint protection solutions capable of detecting anomalous behavior indicative of exploitation. Disable or limit unnecessary services on affected devices to reduce attack surface. Regularly audit device configurations and logs for signs of compromise. For openWRT users, consider upgrading to newer, patched firmware versions or applying community patches if official updates are delayed. Finally, implement robust vulnerability management processes to track and remediate such embedded device vulnerabilities proactively.