Samsung Galaxy DSP Driver Arbitrary ELF Library Loading Vulnerability (CVE-2021-25371) Analysis and Mitigation Guide

1. Vulnerability Overview & Root Cause

This vulnerability (CVE-2021-25371) exists in the DSP (Digital Signal Processor) driver of Samsung mobile devices. The root cause lies in the driver's failure to properly validate the integrity and cryptographic signatures of ELF (Executable and Linkable Format) libraries passed from user space before loading them. This allows a local attacker with high privileges (PR:H) to load unverified, malicious ELF files directly into the DSP subsystem.

2. Exploitation Mechanics & Attack Scenario

To exploit this vulnerability, an attacker must first gain high privileges (such as system or root access) on the target device through other local exploits or malicious applications. Once elevated, the attacker writes a malicious ELF shared library (.so file) to the local filesystem. The attacker then triggers the vulnerable DSP driver's ioctl interface or system calls, passing the path of the malicious library. Because the driver lacks signature verification, it loads and executes the library within the isolated DSP memory context, allowing arbitrary code execution outside the standard Android OS security boundaries.

3. Infrastructure & Business Impact

This vulnerability is cataloged in CISA's Known Exploited Vulnerabilities (KEV), indicating active exploitation in the wild. Because the DSP subsystem operates beneath the standard Android framework, malicious code running inside the DSP can evade detection by mobile Endpoint Detection and Response (EDR) agents. This poses a severe threat to enterprise environments, potentially allowing attackers to establish persistent backdoors, intercept sensitive communications, and exfiltrate confidential corporate data.