CVE-2025-20733 is a heap overflow vulnerability classified under CWE-122, affecting multiple MediaTek wireless chipset models including MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986. The root cause is an incorrect bounds check in the WLAN AP driver, which allows an out-of-bounds write to heap memory. This flaw can be triggered by a local user with execution privileges on the device, without requiring any user interaction, enabling local privilege escalation. The vulnerability affects SDK releases up to version 7.6.7.2 and openWRT versions 19.07 and 21.02, which are commonly used in embedded wireless devices and routers. The CVSS v3.1 score of 7.8 reflects high impact on confidentiality, integrity, and availability, with low attack complexity and limited privileges required. Although no public exploits have been reported yet, the vulnerability poses a significant risk due to the widespread deployment of affected MediaTek chipsets in consumer and enterprise wireless equipment. The issue is tracked internally by MediaTek as MSV-4138 and patched under WCNCR00441509, though no public patch links are currently provided. The vulnerability could allow attackers to execute arbitrary code with elevated privileges, potentially leading to full device compromise, data leakage, or denial of service.

The vulnerability allows local users to escalate privileges on devices running affected MediaTek chipsets, potentially leading to full system compromise. This can result in unauthorized access to sensitive data, manipulation or disruption of wireless communications, and persistent control over network infrastructure components. Given the use of these chipsets in a wide range of wireless access points and embedded devices globally, exploitation could impact enterprise networks, ISPs, and consumer environments. The compromise of network devices could facilitate lateral movement within corporate networks, interception or modification of network traffic, and disruption of critical services. The high severity and ease of exploitation without user interaction increase the risk of rapid exploitation once public exploits become available. Organizations relying on these chipsets in their infrastructure face risks to confidentiality, integrity, and availability, potentially affecting business continuity and data privacy compliance.

Organizations should immediately inventory devices using the affected MediaTek chipsets and verify firmware versions against the vulnerable SDK and openWRT releases. Apply official patches from MediaTek or device vendors as soon as they are released. If patches are not yet available, consider temporary mitigations such as restricting local user access to affected devices, disabling unnecessary WLAN AP driver features, or isolating vulnerable devices within segmented network zones to limit potential exploitation. Monitor device logs and network traffic for unusual activity indicative of exploitation attempts. Engage with vendors to obtain timely updates and verify patch applicability. For openWRT users, upgrade to versions beyond 21.02 once patched builds are available. Implement strict access controls and employ endpoint protection solutions that can detect anomalous behavior related to privilege escalation. Regularly review and update security policies to minimize local user privileges on network devices.