CVE-2025-20741 is a heap overflow vulnerability identified in the wlan 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 an out-of-bounds write to heap memory. This vulnerability is classified under CWE-122 (Heap-based Buffer Overflow). Exploitation requires the attacker to have already obtained System-level privileges on the affected device, but no user interaction is necessary. Successful exploitation can lead to local escalation of privilege, enabling an attacker to execute arbitrary code with elevated privileges, potentially compromising the confidentiality, integrity, and availability of the system. The affected software versions include MediaTek SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02, which are commonly used in embedded devices and wireless access points. The CVSS v3.1 base score is 6.7, reflecting a medium severity with high impact on confidentiality, integrity, and availability, but limited by the requirement for high privileges and local access. No public exploits have been reported to date, and no patch links were provided, indicating that organizations should monitor for vendor updates. The vulnerability is significant for devices that rely on these chipsets for wireless networking, especially in enterprise and telecom environments.

For European organizations, this vulnerability poses a risk primarily to network infrastructure devices such as wireless access points, routers, and embedded systems that incorporate the affected MediaTek chipsets. An attacker with existing system-level access could exploit this flaw to escalate privileges further, potentially gaining full control over the device. This could lead to interception or manipulation of network traffic, disruption of wireless services, or use of compromised devices as pivot points for lateral movement within corporate networks. The impact is particularly critical for telecom providers, ISPs, and enterprises with large-scale wireless deployments. Given the widespread use of openWRT and MediaTek chipsets in consumer and industrial networking equipment, the vulnerability could affect a broad range of devices. The absence of required user interaction facilitates stealthy exploitation once local access is achieved. Although no exploits are currently known in the wild, the potential for privilege escalation makes timely mitigation essential to prevent future attacks.

Organizations should prioritize the following mitigation steps: 1) Inventory all network devices and embedded systems to identify those using the affected MediaTek chipsets and software versions (SDK 7.6.7.2 and earlier, openWRT 19.07 and 21.02). 2) Apply vendor-provided patches or firmware updates as soon as they become available; monitor MediaTek advisories and openWRT releases closely. 3) Restrict local administrative access to devices with these chipsets, enforcing strong authentication and limiting access to trusted personnel only. 4) Employ network segmentation to isolate critical wireless infrastructure from general user networks, reducing the risk of local privilege escalation spreading. 5) Monitor device logs and network traffic for unusual activity indicative of exploitation attempts. 6) Consider upgrading to newer hardware or software versions that do not contain this vulnerability. 7) Implement strict patch management and vulnerability scanning processes focused on embedded and IoT devices. These targeted actions go beyond generic advice by focusing on the specific affected components and the exploitation context.