CVE-2025-20737 is a stack overflow vulnerability identified in the WLAN Access Point (AP) driver code 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, which leads to an out-of-bounds write on the stack (CWE-121). This memory corruption flaw can be exploited by a local attacker who already has user-level execution privileges on the device to escalate their privileges to a higher level, potentially root or kernel-level. The vulnerability does not require user interaction, which means once the attacker has local access, exploitation can be automated or triggered without further user actions. 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 routers. Although no public exploits have been reported yet, the vulnerability poses a significant risk due to the critical nature of privilege escalation vulnerabilities in networking hardware. The flaw could allow attackers to compromise device integrity, manipulate network traffic, or establish persistent footholds within affected systems. The vulnerability was reserved in November 2024 and published in November 2025, with no CVSS score assigned yet. The lack of remote exploitation vector limits the attack surface to local users or attackers who have gained initial access. However, the widespread use of MediaTek chipsets in consumer and enterprise networking equipment increases the potential impact.

For European organizations, this vulnerability could have serious implications, especially for those relying on networking equipment or embedded devices powered by the affected MediaTek chipsets. Successful exploitation could allow attackers to escalate privileges locally, potentially leading to full device compromise. This could result in unauthorized access to sensitive network data, disruption of network services, or use of compromised devices as pivot points for lateral movement within corporate networks. Telecommunications providers, ISPs, and enterprises using openWRT-based routers or devices with MediaTek chipsets are particularly at risk. The impact extends to the confidentiality, integrity, and availability of network infrastructure, potentially affecting critical communications and data flows. Given the vulnerability requires local execution privileges, initial compromise vectors might include phishing, insider threats, or exploitation of other vulnerabilities to gain local access. The absence of user interaction for exploitation increases the risk of automated or stealthy attacks once local access is obtained. The potential for widespread impact is heightened by the common deployment of these chipsets in consumer and industrial networking devices across Europe.

Organizations should immediately inventory their network infrastructure and embedded devices to identify those using the affected MediaTek chipsets and software versions. Where possible, update to patched versions of the MediaTek SDK and openWRT firmware once available. Until patches are released, implement strict access controls to limit local user access to trusted personnel only, and monitor for unusual local activity on devices. Employ network segmentation to isolate vulnerable devices from critical systems and sensitive data. Use endpoint detection and response (EDR) tools to detect anomalous behavior indicative of privilege escalation attempts. Disable or restrict unnecessary services and interfaces that could provide local access to attackers. For openWRT devices, consider applying custom mitigations such as kernel hardening or memory protection features if patching is delayed. Engage with vendors and suppliers to obtain timely updates and verify patch applicability. Finally, conduct regular security audits and penetration testing focused on local privilege escalation vectors to proactively identify and remediate weaknesses.