CVE-2025-20796: Google Android Privilege Escalation Flaw

CVE-2025-20796 Overview

CVE-2025-20796 is an out-of-bounds write vulnerability affecting the imgsys component in MediaTek chipsets running on Google Android devices. The vulnerability stems from improper input validation, which could allow a local attacker who has already obtained System privileges to escalate their access further. Exploitation requires user interaction, making this a targeted attack vector that combines social engineering with technical exploitation.

Critical Impact

Local privilege escalation through out-of-bounds write in MediaTek image subsystem, enabling attackers with System-level access to gain additional capabilities on affected Android devices.

Affected Products

• Google Android 15.0
• MediaTek MT6989 Chipset
• MediaTek MT8796 Chipset
• MediaTek MT8893 Chipset

Discovery Timeline

• 2026-01-06 - CVE-2025-20796 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-20796

Vulnerability Analysis

This vulnerability exists within the imgsys (image subsystem) component of MediaTek chipsets. The image subsystem handles image processing operations and is a critical component for multimedia functionality on Android devices. The out-of-bounds write condition occurs due to improper input validation when processing certain data structures within the subsystem.

The vulnerability is classified under CWE-1285 (Improper Validation of Specified Index, Position, or Offset in Input), indicating that the flaw involves insufficient validation of input parameters that specify memory locations or array indices. When exploited, this allows an attacker to write data beyond the intended memory boundaries, potentially corrupting adjacent memory structures or overwriting critical data.

Root Cause

The root cause of CVE-2025-20796 lies in insufficient input validation within the MediaTek imgsys driver. When the subsystem processes input data, it fails to properly validate index or offset values before using them to access memory. This allows specially crafted input to cause the system to write data to unintended memory locations.

The vulnerability is tracked internally by MediaTek as Patch ID: ALPS10314745 with Issue ID: MSV-5553. The improper validation allows attackers with existing System privileges to manipulate memory in ways that could enable further privilege escalation or arbitrary code execution within the kernel context.

Attack Vector

The attack requires local access to the device, meaning the attacker must either have physical access or have already compromised the device through another vector to gain System-level privileges. The attack flow involves:

1. Initial Compromise: Attacker must first obtain System privileges through another vulnerability or attack chain
2. User Interaction: The victim must be tricked into performing an action that triggers the vulnerable code path
3. Memory Corruption: Malicious input is sent to the imgsys component, causing an out-of-bounds write
4. Privilege Escalation: The memory corruption is leveraged to escalate privileges beyond the System level

The vulnerability mechanism involves sending specially crafted data to the imgsys component that contains malicious index or offset values. When the component processes this data without proper bounds checking, it writes data beyond the allocated buffer boundaries. This out-of-bounds write can be leveraged to corrupt kernel memory structures or overwrite function pointers, ultimately enabling code execution with elevated privileges. For detailed technical information, refer to the MediaTek Product Security Bulletin.

Detection Methods for CVE-2025-20796

Indicators of Compromise

• Unusual crashes or system instability related to multimedia or image processing operations on affected MediaTek devices
• Kernel panic events or unexpected reboots during image subsystem operations
• Evidence of privilege escalation attempts from System-level processes
• Anomalous memory access patterns in imgsys driver logs

Detection Strategies

• Monitor for unusual system calls or ioctl operations targeting the imgsys driver from System-privileged processes
• Implement kernel integrity monitoring to detect unauthorized memory modifications
• Deploy endpoint detection solutions capable of identifying memory corruption exploitation patterns
• Enable Android kernel audit logging to capture suspicious driver interactions

Monitoring Recommendations

• Enable verbose logging for MediaTek driver components where available
• Monitor for applications attempting to access hardware subsystems with elevated privileges
• Implement behavioral analysis to detect privilege escalation chains
• Review system logs for unexpected imgsys component errors or crashes

How to Mitigate CVE-2025-20796

Immediate Actions Required

• Apply the January 2026 security updates from MediaTek and Google for affected Android devices
• Review and audit devices running affected MediaTek chipsets (MT6989, MT8796, MT8893) with Android 15.0
• Implement network segmentation to limit lateral movement if devices cannot be immediately patched
• Educate users about social engineering risks, as user interaction is required for exploitation

Patch Information

MediaTek has released a security patch addressing this vulnerability, identified by Patch ID: ALPS10314745. The fix is documented in the MediaTek Product Security Bulletin for January 2026. Device manufacturers and OEMs should integrate this patch into their Android security updates. End users should install the latest available security updates from their device manufacturer.

Workarounds

• Restrict installation of applications from untrusted sources to reduce initial compromise vectors
• Implement Mobile Device Management (MDM) policies to enforce security configurations
• Limit user access to device features that may trigger vulnerable code paths
• Monitor device behavior and isolate suspicious devices pending patch availability

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

# Check for MediaTek chipset model
adb shell getprop ro.hardware

# Review system logs for imgsys-related events
adb logcat | grep -i "imgsys"