CVE-2024-20125: Google Android Privilege Escalation Flaw

CVE-2024-20125 Overview

CVE-2024-20125 is an out-of-bounds write vulnerability in the MediaTek video decoder (vdec) component affecting a wide range of MediaTek chipsets used in Android devices. The vulnerability stems from a missing bounds check in the vdec module, which could allow an attacker who has already obtained System privileges to escalate their access further through local exploitation. No user interaction is required for successful exploitation of this vulnerability.

Critical Impact

Attackers with System privileges can leverage this out-of-bounds write to achieve local privilege escalation, potentially gaining kernel-level access on affected Android devices powered by vulnerable MediaTek chipsets.

Affected Products

• Google Android 13.0 and 14.0
• MediaTek MT6xxx series chipsets (including MT6580, MT6761, MT6765, MT6768, MT6779, MT6781, MT6785, MT6789, MT6833, MT6835, MT6853, MT6855, MT6873, MT6877, MT6879, MT6883, MT6885, MT6886, MT6889, MT6893, MT6895, MT6983, MT6985)
• MediaTek MT8xxx series chipsets (including MT8175, MT8195, MT8321, MT8365, MT8370, MT8385, MT8390, MT8395, MT8666, MT8667, MT8673, MT8765, MT8766, MT8768, MT8771, MT8781, MT8786, MT8788, MT8791T, MT8797, MT8798)

Discovery Timeline

• 2024-12-02 - CVE-2024-20125 published to NVD
• 2025-04-22 - Last updated in NVD database

Technical Details for CVE-2024-20125

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption vulnerability class that occurs when software writes data past the boundaries of allocated memory buffers. In the context of the MediaTek vdec (video decoder) component, the vulnerability exists due to insufficient validation of input data or buffer sizes during video decoding operations.

The vdec component is responsible for hardware-accelerated video decoding on MediaTek-powered devices. When processing video streams, the decoder must handle various frame sizes, codec parameters, and metadata. The missing bounds check allows an attacker to craft malicious input that triggers a write operation beyond the intended buffer boundaries, potentially corrupting adjacent memory structures.

Successful exploitation requires that the attacker has already obtained System-level privileges on the device. While this is a significant prerequisite, it represents a realistic attack scenario in multi-stage exploitation chains where an initial compromise grants System access, and this vulnerability is then used to achieve kernel-level privilege escalation for complete device control.

Root Cause

The root cause of CVE-2024-20125 is a missing bounds check in the MediaTek vdec driver. When processing certain video decoding operations, the driver fails to properly validate buffer boundaries before performing write operations. This allows data to be written outside the allocated buffer region, leading to memory corruption.

The vulnerability is tracked internally by MediaTek as Patch ID ALPS09046782 with Issue ID MSV-1728. The affected vdec component is part of the MediaTek multimedia subsystem that handles hardware video decoding acceleration.

Attack Vector

The attack vector for CVE-2024-20125 is local, meaning an attacker must have existing access to the target device. The exploitation flow typically involves:

1. An attacker who has already achieved System-level privileges on the Android device (through a separate vulnerability or compromised application)
2. Triggering the vulnerable code path in the vdec driver by initiating video decoding operations with specially crafted parameters
3. The out-of-bounds write corrupts kernel memory structures or function pointers
4. The attacker gains elevated privileges beyond System level, potentially achieving kernel code execution

The vulnerability does not require any user interaction, making it suitable for automated exploitation once the prerequisite System access is obtained. The technical details of triggering the vulnerable code path involve interacting with the MediaTek video decoder through standard Android media APIs or direct ioctl calls to the vdec driver.

Detection Methods for CVE-2024-20125

Indicators of Compromise

• Unexpected crashes or kernel panics in the vdec or multimedia subsystem on MediaTek-powered Android devices
• Anomalous system calls or ioctl operations targeting the vdec driver from processes with elevated privileges
• Memory corruption artifacts in kernel logs referencing vdec or mediatek multimedia components
• Suspicious applications requesting or utilizing System-level permissions in combination with video decoding functionality

Detection Strategies

• Monitor kernel logs for vdec-related memory access violations or out-of-bounds errors
• Implement runtime integrity checking on kernel memory regions adjacent to vdec driver allocations
• Deploy mobile threat defense solutions capable of detecting privilege escalation attempts on Android devices
• Audit applications with System permissions for unusual video decoding patterns or direct driver interactions

Monitoring Recommendations

• Enable enhanced logging for MediaTek multimedia subsystem operations on managed Android devices
• Implement behavioral analysis to detect processes transitioning from System to kernel-level privileges
• Monitor for attempts to load unsigned or modified kernel modules that could indicate post-exploitation activity
• Track security patch levels across the Android device fleet to identify unpatched systems

How to Mitigate CVE-2024-20125

Immediate Actions Required

• Apply the December 2024 security patches from MediaTek and device OEMs as soon as they become available for your device
• Ensure Android devices are updated to the latest available firmware version from the device manufacturer
• Audit devices in your environment to identify those using vulnerable MediaTek chipsets
• Implement defense-in-depth measures to prevent initial System-level compromise that is a prerequisite for this vulnerability

Patch Information

MediaTek has released a security patch addressing this vulnerability, tracked as Patch ID ALPS09046782. The fix is documented in the MediaTek Security Bulletin December 2024. Device manufacturers (OEMs) are responsible for integrating this patch into their firmware updates and distributing them to end users.

Organizations should work with their device vendors to confirm patch availability and deployment timelines for affected devices. The wide range of affected chipsets spanning both smartphone (MT6xxx) and tablet/IoT (MT8xxx) product lines means that patches may be released on different schedules depending on the device manufacturer.

Workarounds

• Limit System-level permissions to only trusted and necessary applications to reduce the attack surface
• Implement application whitelisting and enhanced vetting for applications requiring elevated privileges
• Consider network segmentation and enhanced monitoring for devices that cannot be immediately patched
• Where possible, disable or restrict access to video decoding functionality on high-security devices until patches are applied

# Verify Android security patch level on device
adb shell getprop ro.build.version.security_patch

# Check for MediaTek chipset information
adb shell cat /proc/cpuinfo | grep Hardware

# List installed patches (requires root)
adb shell pm list packages | grep mediatek