CVE-2025-20645 is an out-of-bounds write vulnerability classified under CWE-787 found in the KeyInstall component of various MediaTek SoCs (System on Chips) including MT6765, MT6768, MT6833, MT6835, MT6853, MT6855, MT6879, MT6886, MT6893, MT6897, MT6983, MT6985, MT6989, and MT8796. This vulnerability arises from a missing bounds check during memory operations, which can cause memory corruption by writing outside the intended buffer boundaries. The flaw exists in devices running Android versions 14.0 and 15.0. An attacker who already has System-level privileges on the device can exploit this vulnerability locally to escalate privileges further, potentially gaining higher system privileges or causing system instability. No user interaction is required for exploitation, making automated or stealthy attacks feasible once System access is obtained. The vulnerability affects confidentiality, integrity, and availability of the system, as it can lead to arbitrary code execution or denial of service. Although no public exploits are known at this time, the presence of a patch ID (ALPS09475476) indicates that MediaTek has addressed the issue internally. The vulnerability's CVSS v3.1 score is 7.8, reflecting high severity due to the combination of local attack vector, low attack complexity, required privileges, and significant impact on system security.

The primary impact of CVE-2025-20645 is local privilege escalation on devices using affected MediaTek chipsets running Android 14.0 or 15.0. An attacker with System privileges can exploit this vulnerability to gain higher privileges, potentially leading to full device compromise, unauthorized access to sensitive data, or disruption of device functionality. This could facilitate further attacks such as installing persistent malware, bypassing security controls, or manipulating system components. The vulnerability threatens confidentiality by enabling unauthorized data access, integrity by allowing unauthorized code execution or modification, and availability by potentially causing system crashes or instability. Organizations deploying devices with these MediaTek chipsets, especially in enterprise or critical infrastructure environments, face increased risk of insider threats or malware leveraging this flaw to escalate privileges and evade detection. The lack of required user interaction increases the risk of automated exploitation in compromised environments.

To mitigate CVE-2025-20645, organizations and device manufacturers should prioritize applying the official patch identified by MediaTek (ALPS09475476) as soon as it becomes available. Until patched, restrict System-level access on affected devices to trusted users and processes only, minimizing the attack surface. Employ strict application whitelisting and privilege management to prevent unauthorized escalation attempts. Monitor device logs and behaviors for signs of abnormal privilege escalations or memory corruption. Use endpoint detection and response (EDR) solutions capable of detecting anomalous local privilege escalation activities. For device manufacturers and integrators, conduct thorough code audits and implement robust bounds checking in memory operations to prevent similar vulnerabilities. Additionally, maintain up-to-date firmware and OS versions and educate users about the risks of granting elevated privileges to untrusted applications or processes.