CVE-2025-21072: Samsung Android Privilege Escalation Flaw

CVE-2025-21072 Overview

CVE-2025-21072 is an out-of-bounds write vulnerability affecting the fingerprint trustlet component in Samsung Android devices. The flaw exists in the metadata decoding process of the fingerprint trustlet prior to SMR Dec-2025 Release 1, allowing local privileged attackers to write data beyond allocated memory boundaries. This vulnerability targets the Trusted Execution Environment (TEE), which is a critical security component responsible for handling sensitive biometric data.

With a CVSS score of 4.4 (Medium severity), this vulnerability requires local access and high privileges to exploit, but successful exploitation could lead to high integrity impact on affected devices.

Critical Impact

Local privileged attackers can exploit this out-of-bounds write vulnerability in the fingerprint trustlet to corrupt memory, potentially compromising the integrity of the Trusted Execution Environment on Samsung Android devices.

Affected Products

• Samsung Android 13.0 (all SMR releases prior to SMR Dec-2025 Release 1)
• Samsung Android 14.0 (all SMR releases prior to SMR Dec-2025 Release 1)
• Samsung Android 15.0 (all SMR releases prior to SMR Dec-2025 Release 1)
• Samsung Android 16.0 (all SMR releases prior to SMR Dec-2025 Release 1)

Discovery Timeline

• December 2, 2025 - CVE-2025-21072 published to NVD
• December 5, 2025 - Last updated in NVD database

Technical Details for CVE-2025-21072

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-bounds Write), occurring within the fingerprint trustlet component that operates within Samsung's Trusted Execution Environment. The flaw manifests during the metadata decoding process, where insufficient bounds checking allows write operations to exceed allocated buffer boundaries.

The CVSS:3.1 vector AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N indicates:

• Attack Vector: Local - requires physical or local access to the device
• Attack Complexity: Low - exploitation is straightforward once access is obtained
• Privileges Required: High - attacker needs elevated system privileges
• User Interaction: None - no user action required
• Scope: Unchanged - impact limited to the vulnerable component
• Confidentiality Impact: None
• Integrity Impact: High - potential for significant data modification
• Availability Impact: None

The EPSS (Exploit Prediction Scoring System) probability is 0.015% (2.3rd percentile), suggesting a relatively low likelihood of exploitation in the wild.

Root Cause

The root cause of CVE-2025-21072 lies in improper boundary validation during metadata decoding operations within the fingerprint trustlet. When processing metadata structures, the trustlet fails to properly validate the size or offset of data being written, allowing an attacker with sufficient privileges to trigger write operations that extend beyond the intended memory allocation. This type of vulnerability in a Trusted Execution Environment component is particularly concerning as it operates in a privileged security context designed to protect sensitive biometric data.

Attack Vector

Exploitation of this vulnerability requires an attacker to first obtain high-level privileges on the target Samsung Android device. Once privileged access is achieved, the attacker can craft malicious metadata that triggers the out-of-bounds write condition during the fingerprint trustlet's decoding process. The attack is local in nature, meaning remote exploitation is not directly possible without first compromising the device through another vector.

The attack flow typically involves:

1. Gaining privileged local access to the Samsung Android device
2. Crafting specially formatted metadata designed to trigger the vulnerable code path
3. Submitting the malicious metadata to the fingerprint trustlet
4. Exploiting the out-of-bounds write to corrupt TEE memory or achieve other malicious objectives

Detection Methods for CVE-2025-21072

Indicators of Compromise

• Unusual activity or errors in fingerprint-related system logs
• Unexpected trustlet crashes or restarts in the Trusted Execution Environment
• Anomalous memory access patterns detected by system integrity monitoring
• Signs of privilege escalation attempts preceding fingerprint subsystem interaction

Detection Strategies

Organizations should implement multiple layers of detection to identify potential exploitation attempts:

System Log Monitoring: Monitor Android system logs for unusual errors or exceptions originating from the fingerprint trustlet or TEE components. Pay particular attention to memory-related errors or unexpected process terminations.

Mobile Device Management (MDM): Deploy MDM solutions capable of detecting firmware version compliance and identifying devices running vulnerable SMR releases. SentinelOne Mobile Threat Defense provides comprehensive visibility into device security posture.

Behavioral Analysis: Implement behavioral monitoring to detect anomalous patterns of privileged application access to biometric subsystems that could indicate exploitation attempts.

Monitoring Recommendations

Security teams should establish continuous monitoring for Samsung devices within their fleet:

1. Firmware Version Tracking: Maintain an inventory of device firmware versions and SMR release levels to identify vulnerable devices
2. Security Event Correlation: Correlate security events from mobile endpoints to detect patterns indicative of local privilege escalation followed by trustlet manipulation
3. Integrity Verification: Where possible, implement periodic integrity verification of critical system components

How to Mitigate CVE-2025-21072

Immediate Actions Required

• Update all affected Samsung Android devices to SMR Dec-2025 Release 1 or later
• Conduct an inventory of all Samsung Android devices to identify those running vulnerable firmware versions
• Prioritize patching for devices in high-security environments or those with access to sensitive data
• Implement enhanced monitoring on devices pending patch deployment
• Review and restrict applications with elevated privileges that could be leveraged for exploitation

Patch Information

Samsung has addressed this vulnerability in the SMR Dec-2025 Release 1 security update. The patch is available through Samsung's standard update channels. Organizations should consult Samsung's official security advisory at https://security.samsungmobile.com/securityUpdate.smsb?year=2025&month=12 for detailed patch information and device-specific guidance.

To verify patch status, check the device's security patch level:

• Navigate to Settings > About phone > Software information
• Verify the Android security patch level shows December 2025 or later

Workarounds

As this vulnerability resides in the Trusted Execution Environment's fingerprint trustlet, there are limited workarounds available without applying the official patch. However, organizations can implement the following risk reduction measures while awaiting patch deployment:

1. Limit Privileged Applications: Audit and minimize applications running with elevated privileges that could potentially be leveraged to exploit this vulnerability
2. Enforce Device Encryption: Ensure full device encryption is enabled to limit the impact of potential integrity compromises
3. Network Segmentation: Isolate vulnerable devices from sensitive network resources until patched
4. User Awareness: Educate users about physical device security to prevent local access by unauthorized parties

# Verify Android security patch level via ADB
adb shell getprop ro.build.version.security_patch
# Expected output for patched devices: 2025-12-01 or later