CVE-2021-25371

What it actually does

This is a local privilege-escalation and code-execution weakness in the Samsung DSP driver on affected Android/Samsung Exynos devices. Before the SMR Mar-2021 Release 1 security update, the driver allowed an attacker with already-high local privileges to load arbitrary ELF libraries into the digital signal processor. Successful exploitation can result in attacker-controlled code running in the DSP execution environment, potentially compromising confidentiality, integrity, and availability of data or functions handled by the DSP, including media, signal-processing, sensor, or device-specific workloads.

Why it matters to the business

Compromised devices may allow an attacker who has already gained significant local access to deepen control, evade some normal application-layer protections, access sensitive device-handled data, tamper with device behavior, or destabilize devices. Because this issue is listed in CISA KEV with known exploitation in the wild and a past remediation deadline of 2023-07-20, organizations managing affected Samsung/Android devices should treat unpatched devices as high-priority exposure even though the EPSS score is low and stable.

How an attack unfolds

An attacker first obtains local code execution on an affected Android device with sufficiently high privileges, commonly through a separate exploit chain, malicious privileged component, compromised management channel, or abuse of an already-privileged process. The attacker then interacts with the vulnerable Samsung DSP driver and supplies or references an attacker-controlled ELF library. Due to insufficient enforcement in the pre-SMR Mar-2021 Release 1 driver, the library is accepted and loaded into the DSP environment. Once loaded, the attacker's code executes in the DSP context, allowing manipulation of DSP-handled operations, access to sensitive data processed by the DSP, possible concealment from standard user-space monitoring, and potential device instability or denial of service.

How to fix it

Apply the Samsung Mobile Security Release SMR Mar-2021 Release 1 or later for affected Samsung devices and ensure affected Exynos-based Android devices are running vendor firmware that includes the DSP driver fix. Where mobile device management is available, enforce minimum Android/Samsung security patch levels at or after March 2021 for affected models, block access for noncompliant devices, and retire devices that no longer receive vendor security updates. If immediate patching is not possible, reduce exposure by restricting installation of untrusted applications, disabling developer/debug features where feasible, enforcing device integrity checks, and limiting access to sensitive enterprise resources from unpatched devices.

How to confirm the fix worked

Confirm the device reports a Samsung/Android security patch level that includes SMR Mar-2021 Release 1 or later and verify the exact firmware build against vendor advisories for the affected device model and chipset. For managed fleets, query MDM/UEM inventory for Samsung model, Exynos chipset generation where available, Android security patch level, and firmware build; flag devices below the March 2021 Samsung security update or devices with unknown/no-longer-supported firmware. Validate that noncompliant devices are blocked or quarantined from sensitive services. Where forensic validation is needed, compare DSP driver and firmware component versions against known-good vendor images for the patched release.

Typical attack path

1. Gain local execution on an affected Samsung/Android device through another vulnerability, malicious application path, or compromised privileged process.
2. Escalate or operate with the high local privileges required to access the vulnerable DSP driver interface.
3. Place or stage an attacker-controlled ELF library on the device.
4. Invoke the vulnerable DSP driver functionality to load the arbitrary ELF library into the DSP.
5. Execute attacker-controlled code in the DSP context.
6. Use DSP-level execution to tamper with signal-processing workloads, access sensitive device-handled data, support further persistence/evasion, or crash/degrade the device.

How to detect it

Detection should focus on evidence of a broader local compromise because exploitation requires high local privileges and may not leave a unique, reliable application-layer signature. Review MDM/UEM, mobile threat defense, EDR, and Android telemetry for affected Samsung/Exynos devices that are below the March 2021 Samsung security patch level and show signs of rooting, privilege escalation, bootloader tampering, SELinux enforcement changes, suspicious native binaries, or abnormal privileged process behavior. On devices with available logs, examine Android logcat, kernel logs, vendor crash logs, tombstones, and DSP/firmware crash reports for unusual DSP driver interactions, repeated DSP subsystem crashes, unexpected ELF/library loading activity, or privileged processes accessing DSP-related device nodes. Investigate any unpatched affected device associated with threat-actor activity, unknown privileged APKs, sideloaded native payloads, or unexplained device instability. Because public reporting does not provide stable exploit-specific strings, absence of these artifacts should not be considered proof that exploitation did not occur.

What your security team should do

• Prioritize remediation of any affected Samsung Exynos devices because the vulnerability is in CISA KEV and has documented exploitation in the wild.
• Enforce a minimum Samsung/Android security patch level at or after SMR Mar-2021 Release 1 for affected devices through MDM/UEM policy.
• Identify and quarantine devices that cannot prove a patched firmware build or that are no longer supported by the vendor.
• Review mobile threat defense, EDR, MDM, and device compliance telemetry for signs of privileged process abuse, rooting, suspicious native binaries, or unexpected access to DSP-related device interfaces.
• Treat detection as exploit-chain focused: investigate any unpatched affected device that also shows signs of rooting, privilege escalation, sideloaded privileged apps, unusual native code execution, or security control tampering.
• Reduce attack surface by blocking untrusted app installation, disabling developer options and USB debugging where operationally feasible, and enforcing application allowlisting for high-risk users.