CVE-2025-20742 is a heap overflow vulnerability classified under CWE-122 found in the WLAN AP driver of several MediaTek chipsets, specifically MT6890, MT7603, MT7615, MT7622, MT7915, MT7916, MT7981, and MT7986. The vulnerability is caused by an incorrect bounds check in the driver code, which allows an out-of-bounds write to heap memory. This memory corruption can be exploited remotely by an attacker in wireless proximity (adjacent network) to escalate privileges on the device without requiring any additional execution privileges or user interaction. The flaw affects SDK release 7.6.7.2 and earlier versions and OpenWrt 19.07 and 21.02 builds for MT6890. The vulnerability impacts confidentiality, integrity, and availability by potentially allowing attackers to execute arbitrary code or disrupt device operation. The CVSS 3.1 vector (AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) indicates that the attack requires adjacent network access with low attack complexity and low privileges but no user interaction. Although no exploits have been reported in the wild, the vulnerability poses a significant risk to devices using these chipsets, commonly found in wireless access points and routers. MediaTek has assigned Patch ID WCNCR00432680 and Issue ID MSV-3949 for remediation, though no public patch links are currently available.

This vulnerability can lead to remote privilege escalation on wireless access points and routers using affected MediaTek chipsets, potentially allowing attackers to gain control over network infrastructure devices. Such control can compromise network confidentiality by intercepting or manipulating traffic, integrity by injecting malicious data or commands, and availability by causing device crashes or denial of service. Organizations relying on these devices for critical network connectivity, especially in enterprise, ISP, or IoT environments, face risks of lateral movement, persistent footholds, and disruption of services. The requirement for only adjacent network access lowers the barrier for exploitation in environments with wireless coverage, such as corporate campuses, public Wi-Fi, or residential areas. The absence of user interaction further increases the threat as attacks can be automated and stealthy. The broad range of affected chipsets and firmware versions amplifies the scope of impact globally.

Organizations should immediately inventory devices using the affected MediaTek chipsets and firmware versions. Once available, apply the official patches from MediaTek (Patch ID WCNCR00432680) or updated OpenWrt releases that address this vulnerability. Until patches are deployed, implement network segmentation to isolate vulnerable wireless access points from sensitive network segments. Enforce strong wireless security protocols (WPA3 if possible) to limit unauthorized adjacent access. Monitor wireless network traffic for anomalous activity indicative of exploitation attempts, such as unusual privilege escalations or memory corruption indicators. Disable or restrict unnecessary wireless services and interfaces on affected devices. Employ intrusion detection/prevention systems (IDS/IPS) tuned to detect heap overflow exploitation patterns targeting MediaTek WLAN drivers. Regularly update device firmware and maintain a vulnerability management program to quickly respond to emerging threats. Engage with vendors for timely security advisories and patches.