CVE-2025-20748 is a buffer overflow vulnerability classified under CWE-120, affecting the WLAN AP driver in several MediaTek chipsets: MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986. The root cause is an incorrect bounds check in the driver code that leads to an out-of-bounds write operation. This flaw can be exploited locally by an attacker who already possesses System-level privileges on the device, enabling escalation of privileges beyond the current level. The vulnerability does not require any user interaction, increasing the risk of automated or stealthy exploitation once initial access is obtained. The affected software versions include SDK release 7.6.7.2 and earlier, as well as openWRT versions 19.07 and 21.02, which are commonly used in embedded wireless devices and access points. Although no public exploits have been reported yet, the vulnerability's nature suggests that it could be leveraged to execute arbitrary code or cause denial of service by corrupting memory. The issue was officially published on November 4, 2025, with a patch identified as WCNCR00432679, though no direct patch links are provided. Given the widespread use of MediaTek chipsets in consumer and enterprise wireless equipment, this vulnerability poses a significant risk to network security, particularly in environments where devices run vulnerable firmware and attackers have already gained system-level access. The vulnerability's exploitation could undermine device integrity and confidentiality, potentially facilitating lateral movement or persistence within networks.

For European organizations, this vulnerability presents a risk primarily in environments using MediaTek-based wireless access points or embedded devices running the affected SDK or openWRT versions. The ability to escalate privileges locally without user interaction means that once an attacker gains system-level access—potentially through other vulnerabilities or misconfigurations—they could exploit this flaw to gain deeper control over the device. This could lead to unauthorized code execution, manipulation of wireless traffic, or disruption of network services. Critical infrastructure sectors, enterprises with extensive wireless deployments, and service providers relying on MediaTek hardware could face increased risk of compromise or service degradation. The vulnerability could also facilitate advanced persistent threats by enabling attackers to maintain or escalate privileges stealthily. Given the prevalence of openWRT in customized networking solutions across Europe, particularly in Germany, France, and the UK, the impact could be widespread if patches are not applied promptly. The absence of known exploits in the wild currently limits immediate risk but does not diminish the potential severity if weaponized.

1. Immediately identify and inventory all devices using MediaTek chipsets MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986, especially those running SDK release 7.6.7.2 or earlier and openWRT versions 19.07 or 21.02. 2. Apply the vendor-provided patch referenced as WCNCR00432679 as soon as it becomes available; coordinate with device manufacturers or firmware providers if direct patches are not accessible. 3. For openWRT devices, upgrade to the latest stable releases beyond 21.02 that include the fix or apply community patches addressing this vulnerability. 4. Implement strict access controls and monitoring to prevent unauthorized system-level access, as exploitation requires existing System privileges. 5. Conduct regular firmware audits and vulnerability scans focusing on embedded wireless devices to detect outdated or vulnerable versions. 6. Employ network segmentation to isolate critical wireless infrastructure and limit lateral movement opportunities. 7. Monitor device logs and network traffic for anomalous behavior indicative of exploitation attempts. 8. Engage with vendors and security communities to stay informed about exploit developments and additional mitigations. 9. Consider deploying endpoint detection and response (EDR) solutions capable of detecting privilege escalation attempts on embedded devices where feasible.