CVE-2025-20671 Overview
CVE-2025-20671 is an out-of-bounds write vulnerability in the MediaTek thermal driver used across Android devices. The flaw stems from a race condition in the driver's handling of thermal management operations. Successful exploitation enables local escalation of privilege, but the attacker must already hold System-level privileges on the target device. User interaction is not required for exploitation. MediaTek tracks this issue as Patch ID ALPS09698599 and Issue ID MSV-3228. The vulnerability affects a wide range of MediaTek chipsets shipped in Android 14 and Android 15 devices.
Critical Impact
An attacker with System privilege can trigger a memory corruption condition in the thermal driver to escalate to higher kernel-level privileges without user interaction.
Affected Products
- Google Android 14.0 and 15.0 running on affected MediaTek chipsets
- MediaTek chipsets: MT2718, MT6878, MT6897, MT6899, MT6989, MT6991
- MediaTek chipsets: MT8196, MT8391, MT8676, MT8678
Discovery Timeline
- 2025-05-05 - CVE-2025-20671 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-20671
Vulnerability Analysis
CVE-2025-20671 is an out-of-bounds write [CWE-787] triggered by a race condition inside the MediaTek thermal driver. The thermal subsystem manages device temperature sensors and throttling policies on MediaTek system-on-chip (SoC) platforms. Concurrent access to a shared thermal data structure from multiple execution contexts allows an attacker to manipulate state between a validation check and the subsequent write operation. This time-of-check to time-of-use (TOCTOU) window enables writes beyond an allocated buffer boundary. The corrupted memory can be leveraged to modify kernel structures and elevate privileges from System to kernel context.
Root Cause
The root cause is insufficient synchronization around a bounded write operation in the thermal driver. When two threads access the same thermal state concurrently, one thread can alter the size or index parameters that a second thread has already validated. The second thread then proceeds to write using stale bounds, resulting in an out-of-bounds write past the intended buffer.
Attack Vector
Exploitation requires local access with System privilege already obtained on the device. This typically means the attacker has compromised a privileged Android system service or app. The attacker then interacts with the thermal driver interface concurrently from multiple threads to win the race and trigger the out-of-bounds write. The attack complexity is high because timing the race reliably requires precise control of scheduling.
The vulnerability manifests in the MediaTek thermal driver's concurrent request handling. See the MediaTek Product Security Bulletin for vendor-provided technical details.
Detection Methods for CVE-2025-20671
Indicators of Compromise
- Unexpected kernel crashes or panics referencing thermal driver symbols on affected MediaTek devices
- Android system services running with System privilege spawning threads that repeatedly call thermal management ioctls
- Kernel log entries showing memory corruption warnings originating in the thermal subsystem
Detection Strategies
- Monitor Android dmesg and kernel ring buffer output for KASAN or slab corruption reports tied to thermal driver functions
- Track processes with SYSTEM UID making anomalous or high-frequency calls to thermal sysfs and ioctl interfaces
- Correlate device reboot events with prior privileged process activity targeting /sys/class/thermal or MediaTek thermal nodes
Monitoring Recommendations
- Enroll affected devices into mobile threat defense telemetry to capture kernel-level anomalies and privilege transitions
- Baseline normal thermal driver interaction patterns from OEM system services and alert on deviations
- Ingest Android security patch level attestations into central logging to confirm affected devices have received May 2025 or later patches
How to Mitigate CVE-2025-20671
Immediate Actions Required
- Apply the MediaTek security patch identified as ALPS09698599 through the device OEM's firmware update channel
- Confirm devices report an Android security patch level of May 2025 or later on affected MediaTek chipsets
- Restrict installation of applications capable of obtaining System privilege and audit sideloaded privileged services
Patch Information
MediaTek addressed CVE-2025-20671 in Patch ID ALPS09698599 (Issue ID MSV-3228), published in the May 2025 MediaTek Product Security Bulletin. Device manufacturers integrate this patch into their monthly Android security updates. Consult the MediaTek Product Security Bulletin and the corresponding OEM firmware release notes to verify coverage for a specific device model.
Workarounds
- No official workaround is published; the vendor patch is the authoritative remediation
- Enforce mobile device management (MDM) policies that block unmanaged privileged applications on affected chipsets
- Isolate devices that cannot receive the May 2025 or later security patch level from sensitive networks and data
# Verify Android security patch level on an affected device
adb shell getprop ro.build.version.security_patch
# Confirm MediaTek chipset model
adb shell getprop ro.hardware
adb shell getprop ro.board.platform
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
