CVE-2025-20738 is a stack overflow vulnerability identified in the wlan AP driver of multiple MediaTek chipsets widely used in wireless access points and embedded devices. The root cause is an incorrect bounds check that permits an out-of-bounds write on the stack, which can corrupt memory and potentially allow an attacker to escalate privileges locally. Since exploitation requires the attacker to have already obtained System-level privileges, the vulnerability primarily serves as a means to deepen control or persistence on compromised devices. The flaw does not require user interaction, increasing its risk in automated or unattended environments. The affected MediaTek chipsets (MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, MT7986) are integrated into various wireless routers and IoT devices, many of which run SDK release 7.6.7.2 or earlier and openWRT versions 19.07 and 21.02. The vulnerability is classified under CWE-121, indicating a classic stack-based buffer overflow scenario. While no public exploits have been reported, the vulnerability’s presence in widely deployed wireless infrastructure components makes it a significant concern. The absence of a CVSS score requires a severity assessment based on impact and exploitability factors. MediaTek has acknowledged the issue and assigned it an internal patch ID (WCNCR00435342), but no public patch links are currently available.

For European organizations, this vulnerability poses a risk primarily in environments where MediaTek-based wireless access points or embedded devices are deployed, especially those running vulnerable SDK or openWRT versions. Successful exploitation could allow attackers who have already compromised a system to escalate privileges, potentially leading to full device compromise, unauthorized configuration changes, or persistent backdoors in network infrastructure. This could disrupt network availability, compromise confidentiality of internal communications, and undermine integrity of network management. Given the widespread use of MediaTek chipsets in consumer and enterprise-grade wireless equipment, organizations relying on such devices for critical connectivity or IoT deployments could face increased risk of lateral movement and deeper network infiltration. The lack of required user interaction facilitates automated exploitation in compromised environments. While no exploits are currently known in the wild, the vulnerability’s presence in foundational network components makes it a strategic target for attackers aiming to maintain or escalate footholds in European networks.

Organizations should first inventory their network devices to identify those using affected MediaTek chipsets and running vulnerable SDK or openWRT versions. Immediate mitigation involves applying vendor-supplied patches once available; until then, consider upgrading to newer firmware versions that address this issue. Network segmentation should be enforced to limit access to management interfaces of affected devices, reducing the risk that attackers with lower privileges can reach vulnerable components. Employ strict access controls and monitoring on devices with System-level access to detect and prevent unauthorized privilege escalations. Disable or restrict unnecessary services on wireless access points to minimize attack surface. For openWRT deployments, upgrading to versions beyond 21.02 or applying community patches addressing this vulnerability is recommended. Additionally, implement host-based intrusion detection systems (HIDS) and anomaly detection to identify suspicious behavior indicative of exploitation attempts. Regularly audit device configurations and logs for signs of compromise. Finally, maintain a robust patch management process to rapidly deploy fixes when MediaTek releases official updates.