CVE-2025-20731 is a heap overflow vulnerability classified under CWE-122, found in the WLAN Access Point (AP) driver of several MediaTek chipsets including MT6890, MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986. The vulnerability stems from an incorrect bounds check in the driver code, which leads to an out-of-bounds write operation on the heap. This memory corruption can be exploited to escalate privileges locally, but only if the attacker has already obtained System-level privileges and the OceReducedNeighborReport feature is disabled. The flaw does not require any user interaction, increasing the risk of automated or stealthy exploitation. 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 devices and wireless routers. Although no public exploits are currently reported, the vulnerability's nature suggests that successful exploitation could allow attackers to execute arbitrary code or manipulate system behavior at a high privilege level, potentially compromising device security and network integrity. The vendor has acknowledged the issue (Issue ID MSV-4140) and assigned a patch ID (WCNCR00441511), but no patch links are currently provided. The absence of a CVSS score requires an independent severity assessment based on the technical details and potential impact.

For European organizations, this vulnerability poses a significant risk to the security of wireless infrastructure devices that utilize affected MediaTek chipsets. Successful exploitation could allow attackers with existing System privileges to escalate their access further, potentially gaining full control over the device. This could lead to unauthorized configuration changes, interception or manipulation of network traffic, and pivoting to other internal systems. Given that many embedded devices and wireless access points in enterprise, industrial, and consumer environments use these chipsets, the scope of impact is broad. The vulnerability could disrupt availability if exploited to crash devices or degrade performance. Confidentiality and integrity of network communications could also be compromised, especially in environments relying on these devices for secure wireless connectivity. The lack of required user interaction facilitates stealthy attacks, increasing the threat to critical infrastructure and sensitive data within European organizations. Additionally, openWRT is widely used in custom and commercial router deployments, amplifying the potential exposure.

European organizations should immediately inventory their network devices and embedded systems to identify those using the affected MediaTek chipsets and software versions (SDK release 7.6.7.2 and earlier, openWRT 19.07 and 21.02). They should monitor MediaTek and openWRT official channels for patches corresponding to Patch ID WCNCR00441511 and apply updates promptly once available. Until patches are deployed, organizations should consider disabling or verifying the configuration of the OceReducedNeighborReport feature to reduce exploitation risk. Network segmentation and strict access controls should be enforced to limit local access to vulnerable devices, as exploitation requires System-level privileges. Employing host-based intrusion detection systems (HIDS) and monitoring for anomalous behavior on wireless APs can help detect exploitation attempts. Firmware integrity checks and secure boot mechanisms should be utilized to prevent unauthorized code execution. Additionally, organizations should review and harden device management interfaces, restrict administrative access, and ensure strong authentication to reduce the likelihood of privilege escalation prerequisites being met.