CVE-2025-20765: Linuxfoundation Yocto DOS Vulnerability

CVE-2025-20765 Overview

CVE-2025-20765 is a race condition vulnerability discovered in the Android Exception Engine (AEE) daemon affecting numerous MediaTek chipsets and associated operating systems including Google Android, Linux Foundation Yocto, and OpenWrt. The vulnerability exists within the aee daemon component and can be exploited by an attacker who has already obtained System-level privileges to trigger a local denial of service condition, resulting in a system crash.

The vulnerability is classified as CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and CWE-415 (Double Free), indicating that the race condition may lead to memory corruption through improper resource management.

Critical Impact

Local denial of service leading to system crash on devices powered by affected MediaTek chipsets. Requires System privilege but no user interaction for exploitation.

Affected Products

• Google Android 14.0, 15.0, and 16.0
• Linux Foundation Yocto 4.0
• OpenWrt 21.02.0 and 23.05.0
• MediaTek MT67xx Series (MT6739, MT6761, MT6765, MT6768, MT6781, MT6789, MT6833, MT6835, MT6853, MT6855, MT6877, MT6878, MT6879, MT6880, MT6883, MT6885, MT6886, MT6889, MT6890, MT6893, MT6895, MT6897, MT6899, MT6980D, MT6983, MT6985, MT6989, MT6990, MT6991)
• MediaTek MT81xx Series (MT8113, MT8115, MT8139, MT8163, MT8168, MT8169, MT8183, MT8186, MT8188)
• MediaTek MT85xx Series (MT8512, MT8516, MT8518, MT8519, MT8532)
• MediaTek MT86xx Series (MT8676, MT8678, MT8695, MT8696, MT8698)
• MediaTek MT27xx Series (MT2718, MT2737)

Discovery Timeline

• 2025-12-02 - CVE-2025-20765 published to NVD
• 2025-12-03 - Last updated in NVD database

Technical Details for CVE-2025-20765

Vulnerability Analysis

This vulnerability carries a CVSS 3.1 base score of 4.7 (Medium severity) with the vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H. The scoring indicates:

• Attack Vector (AV:L): Local access is required to exploit this vulnerability
• Attack Complexity (AC:H): High complexity due to the race condition timing requirements
• Privileges Required (PR:L): Low privileges initially, though System privilege must be obtained beforehand
• User Interaction (UI:N): No user interaction needed for exploitation
• Scope (S:U): The impact is limited to the vulnerable component
• Availability Impact (A:H): High impact on system availability through denial of service

The EPSS (Exploit Prediction Scoring System) score is 0.005% with a percentile of 17.7%, indicating a relatively low probability of exploitation in the wild.

Root Cause

The root cause of CVE-2025-20765 lies in improper synchronization within the AEE (Android Exception Engine) daemon when handling concurrent operations. The AEE daemon is responsible for collecting crash information and exception handling on MediaTek-powered devices. When multiple threads or processes access shared resources within the daemon simultaneously without proper locking mechanisms, a race condition occurs.

The associated CWE identifiers suggest that this race condition can lead to a double-free condition (CWE-415), where memory is freed multiple times. This typically happens when:

1. Thread A checks a condition and prepares to free a resource
2. Thread B intervenes and frees the same resource
3. Thread A proceeds to free the already-freed resource

This memory corruption ultimately results in system instability and crashes.

Attack Vector

The attack requires local access to the device and System-level privileges. An attacker who has already compromised a device to obtain System privileges can exploit this vulnerability by manipulating the timing of operations within the AEE daemon.

The attack scenario involves triggering concurrent operations that access shared resources within the daemon at precisely the right moment to cause the race condition. Since the attack complexity is high due to timing requirements, exploitation requires specific conditions to be met, making opportunistic exploitation less likely but targeted attacks feasible.

No user interaction is required once the attacker has obtained the necessary privileges, and the exploitation can be automated once the timing window is understood.

Detection Methods for CVE-2025-20765

Indicators of Compromise

• Unexpected system crashes or reboots with crash dumps pointing to the aee daemon
• Abnormal process behavior or resource contention in AEE-related services
• Kernel panic logs referencing double-free or memory corruption in AEE components
• Repeated system instability on MediaTek-powered devices without apparent cause

Detection Strategies

Organizations should implement monitoring for anomalous behavior in the AEE daemon and related system services. Key detection approaches include:

1. Log Analysis: Monitor system logs for crash dumps, kernel panics, or exception reports related to the aee daemon. Look for patterns indicating memory corruption or synchronization failures.

2. Process Monitoring: Track the behavior of privileged processes that interact with the AEE daemon. Unusual timing patterns or rapid successive calls may indicate exploitation attempts.

3. Memory Integrity Checks: Implement runtime memory integrity monitoring to detect double-free conditions or heap corruption that may result from successful exploitation.

4. Behavioral Analytics: Use endpoint detection solutions to identify anomalous privilege escalation patterns that may precede exploitation attempts.

Monitoring Recommendations

Deploy comprehensive endpoint monitoring on devices running affected MediaTek chipsets. SentinelOne's behavioral AI engine can detect anomalous system behavior patterns associated with race condition exploitation and denial of service attacks.

Implement centralized logging for Android devices in enterprise environments to correlate crash events across the fleet. Configure alerts for repeated system crashes on specific device models known to use affected MediaTek chipsets.

For IoT deployments using OpenWrt or Yocto on MediaTek hardware, establish baseline system stability metrics and alert on deviations that may indicate exploitation attempts or successful attacks.

How to Mitigate CVE-2025-20765

Immediate Actions Required

• Apply MediaTek security patch ALPS10190802 as soon as it becomes available through your device manufacturer or OS vendor
• Monitor for Android security bulletins from device manufacturers that incorporate the MediaTek fix
• Audit systems for unauthorized privilege escalation that may indicate pre-positioning for exploitation
• Implement network segmentation to limit the blast radius of compromised devices
• Review and restrict applications with System-level privileges on affected devices

Patch Information

MediaTek has released a security patch identified as ALPS10190802 (Issue ID: MSV-4833) to address this vulnerability. The patch is documented in the MediaTek Product Security Bulletin for December 2025.

For Android devices, the fix will be distributed through the Android security patch process. Device manufacturers will integrate the MediaTek patch into their firmware updates. Users should ensure their devices are running the latest available firmware that includes the December 2025 security patches.

For Yocto and OpenWrt deployments, check with your distribution maintainers or build the updated MediaTek BSP (Board Support Package) containing the security fix.

Workarounds

Since this vulnerability requires System-level privileges for exploitation, the primary workaround involves hardening privilege management on affected devices:

1. Restrict System Privileges: Audit and minimize the number of applications and services running with System-level privileges on affected devices.

2. SELinux Enforcement: Ensure SELinux is set to enforcing mode on Android devices to limit the ability of compromised applications to escalate privileges.

3. Application Vetting: Implement strict application vetting processes to prevent malicious applications from being installed that might exploit other vulnerabilities to gain System privileges.

4. Device Management: For enterprise deployments, use Mobile Device Management (MDM) solutions to enforce security policies and monitor device health.

# Verify SELinux enforcement status on Android devices
adb shell getenforce
# Expected output: Enforcing

# Check for System-privileged applications
adb shell pm list packages -f | grep -E "priv-app|system"