CVE-2025-20671 is a vulnerability classified under CWE-787 (Out-of-bounds Write) found in the thermal management subsystem of several MediaTek chipsets, including MT2718, MT6878, MT6897, MT6899, MT6989, MT6991, MT8196, MT8391, MT8676, and MT8678. The flaw arises from a race condition that allows an attacker with existing System privileges to perform an out-of-bounds write operation. This memory corruption can lead to local escalation of privileges by corrupting critical data structures or code pointers, potentially allowing the attacker to gain higher privileges or execute arbitrary code within the kernel context. The vulnerability affects devices running Android versions 14.0 and 15.0 that incorporate these chipsets. Exploitation requires the attacker to have System-level privileges already, and no user interaction is needed, which means automated or background attacks are possible once the attacker has initial access. The CVSS v3.1 base score is 6.4, reflecting medium severity with high impacts on confidentiality, integrity, and availability, but mitigated by the requirement for high privileges and high attack complexity. No public exploits have been reported yet, but the presence of a patch ID (ALPS09698599) indicates that fixes are available or forthcoming. The vulnerability was reserved in November 2024 and published in May 2025, indicating recent discovery and disclosure.

The primary impact of CVE-2025-20671 is local privilege escalation on devices using affected MediaTek chipsets running Android 14 or 15. An attacker who has already compromised system-level privileges could exploit this vulnerability to gain kernel-level privileges, potentially leading to full device compromise. This can result in unauthorized access to sensitive data, persistent malware installation, and disruption of device functionality. The out-of-bounds write can also cause system instability or crashes, affecting availability. Since the vulnerability requires existing high privileges, it is less likely to be exploited remotely but poses a significant risk in scenarios where attackers have local access or have compromised lower-level system components. This threat is particularly relevant for mobile devices used in enterprise environments, critical infrastructure, or by high-value targets, where device integrity and confidentiality are paramount.

Organizations and users should apply the official patches provided by MediaTek and device manufacturers as soon as they become available, referencing patch ID ALPS09698599. Until patches are deployed, restrict access to devices to trusted users only and enforce strict privilege separation to prevent unauthorized elevation to System privileges. Employ runtime protections such as kernel address space layout randomization (KASLR) and memory protection mechanisms to reduce exploitation success. Monitor devices for unusual behavior indicative of privilege escalation attempts. For enterprises, implement mobile device management (MDM) solutions to enforce security policies and timely patch deployment. Additionally, conduct regular security audits and vulnerability assessments on devices with affected chipsets to identify potential compromises early. Avoid installing untrusted applications or software that could grant System privileges to attackers.