CVE-2021-25371: Samsung Android DSP Driver RCE Flaw

CVE-2021-25371 Overview

CVE-2021-25371 is a driver vulnerability affecting Samsung mobile devices with Exynos chipsets that allows attackers to load arbitrary ELF libraries inside the Digital Signal Processor (DSP). This vulnerability exists in the DSP driver prior to Samsung's SMR March 2021 Release 1 and has been confirmed as actively exploited in the wild.

Critical Impact
This vulnerability is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed exploitation in real-world attacks. Successful exploitation allows attackers to execute arbitrary code within the DSP context, potentially leading to complete device compromise.

Affected Products

Samsung Android 10.0 (SMR-Jan-2021-R1 and SMR-Feb-2021-R1)
Samsung Android 11.0 (SMR-Jan-2021-R1 and SMR-Feb-2021-R1)
Samsung Exynos 2100 processors
Samsung Exynos 980 processors
Samsung Exynos 9830 processors

Discovery Timeline

2021-03-26 - CVE-2021-25371 published to NVD
2025-10-30 - Last updated in NVD database

Technical Details for CVE-2021-25371

Vulnerability Analysis

This vulnerability affects the DSP driver component on Samsung devices utilizing Exynos chipsets. The flaw allows an attacker with local access and elevated privileges to load arbitrary ELF (Executable and Linkable Format) libraries into the DSP execution environment. The DSP is a specialized processor that handles audio, video, and sensor data processing on mobile devices.

The vulnerability is classified under CWE-912 (Hidden Functionality), indicating the presence of undocumented or hidden functionality in the DSP driver that can be abused by attackers. This architectural weakness enables the loading of malicious libraries that would otherwise be restricted.

Root Cause

The root cause of CVE-2021-25371 lies in insufficient validation and access controls within the Samsung DSP driver. The driver fails to properly verify the legitimacy and integrity of ELF libraries before loading them into the DSP's execution environment. This lack of validation creates a pathway for attackers to inject malicious code into a privileged processor context.

The DSP driver does not implement adequate checks to ensure that only authorized, signed libraries are loaded, allowing attackers with sufficient privileges to bypass security boundaries and execute arbitrary code within the DSP.

Attack Vector

The attack requires local access to the device with high privileges. An attacker who has already achieved elevated access on a Samsung device (through another exploit or malicious application) can leverage this vulnerability to load arbitrary ELF libraries into the DSP. This can be used to:

Establish persistence at the hardware level
Access sensitive data processed by the DSP (audio, sensor data)
Bypass Android's application sandboxing by executing code in the DSP context
Potentially chain with other vulnerabilities for complete device compromise

The vulnerability is particularly concerning because DSP code execution occurs outside the typical Android security model, making detection and remediation more challenging.

Detection Methods for CVE-2021-25371

Indicators of Compromise

Unusual DSP driver activity or unexpected library loading events in system logs
Presence of unauthorized or unsigned ELF libraries in DSP-related directories
Anomalous behavior in audio, video, or sensor processing subsystems
System instability or unexpected resource consumption related to DSP operations

Detection Strategies

Monitor for unusual ioctl calls to the DSP driver interface
Implement file integrity monitoring on DSP-related system directories
Deploy mobile threat detection solutions capable of monitoring driver-level activity
Analyze system logs for unauthorized library loading attempts targeting the DSP

Monitoring Recommendations

Enable comprehensive logging for kernel-level driver interactions
Utilize Samsung Knox security features to detect tampering attempts
Implement endpoint detection and response (EDR) solutions on managed mobile devices
Regularly audit devices for firmware and security patch compliance

How to Mitigate CVE-2021-25371

Immediate Actions Required

Apply Samsung SMR March 2021 Release 1 or later security updates immediately
Verify device firmware versions against affected Exynos chipset models
Isolate or restrict devices that cannot be patched from sensitive networks
Enable Samsung Knox security features for enhanced protection
Monitor CISA KEV catalog for related vulnerabilities and threat intelligence

Patch Information

Samsung addressed this vulnerability in the SMR March 2021 Release 1 security update. The patch includes enhanced validation controls in the DSP driver to prevent unauthorized ELF library loading.

For detailed patch information, refer to the Samsung Mobile Security Portal and Samsung Mobile Security Updates.

Organizations should prioritize patching due to this vulnerability's inclusion in the CISA Known Exploited Vulnerabilities Catalog.

Workarounds

Limit user access to rooted or privileged device operations
Implement mobile device management (MDM) policies to restrict application installation sources
Deploy network segmentation to limit potential lateral movement from compromised devices
Consider temporary device replacement for critical personnel if patches cannot be applied promptly

bash

# Verify Samsung security patch level on Android device
adb shell getprop ro.build.version.security_patch
# Expected output should be 2021-03-01 or later for patched devices