CVE-2025-20936 Overview
CVE-2025-20936 is an improper access control vulnerability in the High-bandwidth Digital Content Protection (HDCP) trustlet on Samsung Android devices. The flaw affects Samsung Android versions 13, 14, and 15 running Security Maintenance Release (SMR) builds prior to SMR Apr-2025 Release 1. A local attacker with shell privilege can leverage the weakness to escalate privileges to root, undermining the Android security model and the isolation guarantees of the TrustZone-based trustlet.
Samsung addressed the issue in the April 2025 Samsung Mobile Security Maintenance Release. The vulnerability is tracked with CWE classification NVD-CWE-noinfo.
Critical Impact
A local attacker with shell access can escalate to root on unpatched Samsung Android 13, 14, and 15 devices, gaining full control over the device.
Affected Products
- Samsung Android 13.0 (SMR builds prior to Apr-2025 Release 1)
- Samsung Android 14.0 (SMR builds prior to Apr-2025 Release 1)
- Samsung Android 15.0 (SMR Jan-2025, Feb-2025, and Mar-2025 Release 1)
Discovery Timeline
- 2025-04-08 - CVE-2025-20936 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-20936
Vulnerability Analysis
The vulnerability resides in the HDCP trustlet, a Trusted Application (TA) that runs inside the ARM TrustZone Trusted Execution Environment (TEE) on Samsung devices. Trustlets are expected to enforce strict access control on the commands they accept from the Rich Execution Environment (REE). In vulnerable Samsung builds, the HDCP trustlet fails to properly restrict which callers can invoke sensitive operations exposed through its command interface.
An attacker who already holds shell privileges — for example, through Android Debug Bridge (ADB) access, a compromised app running in the shell UID, or an earlier bug that yielded shell-level code execution — can reach the HDCP trustlet interface and issue commands the trustlet should reject. Successful exploitation elevates the caller to root, breaking out of the Android permission sandbox.
Root Cause
The root cause is missing or insufficient authorization checks in the HDCP trustlet's command handler. Because the trustlet operates with higher privilege than the Android userspace, any code path it exposes without validating the caller becomes a bridge from the untrusted REE into the trusted domain. This design flaw maps to the broader category of Improper Access Control affecting kernel- and TEE-adjacent components.
Attack Vector
Exploitation requires local access with shell privilege and no user interaction. The attacker interacts with the HDCP trustlet through the standard trustlet communication path used by Android services, sending crafted commands that the trustlet processes without adequate authorization. Because the vulnerability is local, remote exploitation is not possible without first landing shell-level code on the device through a separate flaw, a malicious application, or physical/ADB access.
No public proof-of-concept, exploit code, or CISA Known Exploited Vulnerabilities listing is associated with CVE-2025-20936 at the time of writing.
Detection Methods for CVE-2025-20936
Indicators of Compromise
- Unexpected transitions from the shell UID to root in Android process trees or logcat output.
- Anomalous invocations of HDCP-related trustlet commands from processes that do not normally interact with DRM services.
- Presence of previously unknown binaries or SELinux domain transitions on devices still running pre-April 2025 SMR builds.
Detection Strategies
- Inventory the Samsung Android build number (ro.build.version.security_patch) across managed devices and flag anything older than the 2025-04-01 patch level.
- Use Mobile Device Management (MDM) or Enterprise Mobility Management (EMM) compliance rules to block or quarantine devices below SMR Apr-2025 Release 1.
- Correlate ADB usage, developer-mode activation, and sideloaded applications with devices missing the April 2025 patch level.
Monitoring Recommendations
- Alert on Samsung devices reporting a security_patch value earlier than 2025-04-01.
- Monitor for applications requesting INSTALL_PACKAGES, ADB shell sessions, or debugging tooling on production fleet devices.
- Track attestation results from Android Key Attestation or Samsung Knox Attestation to identify devices whose integrity signals change unexpectedly.
How to Mitigate CVE-2025-20936
Immediate Actions Required
- Apply the April 2025 Samsung Mobile Security Maintenance Release (SMR Apr-2025 Release 1) or later to all affected Samsung Android 13, 14, and 15 devices.
- Enforce MDM policies that block enrollment or network access for devices below the 2025-04-01 Android security patch level.
- Disable ADB and developer options on production devices unless required for supported workflows.
Patch Information
Samsung fixed the improper access control in the HDCP trustlet in the April 2025 Samsung Mobile Security Maintenance Release. Refer to the Samsung Mobile Security Update - April 2025 advisory for build-specific fix details and rollout status across Galaxy device models.
Workarounds
- Restrict installation of untrusted applications through Google Play Protect and MDM allow-lists to reduce the likelihood of an attacker gaining shell-level execution.
- Require Samsung Knox attestation or Android Play Integrity checks before granting access to sensitive enterprise resources from mobile endpoints.
- Retire or isolate legacy devices that will not receive the April 2025 SMR patch on their next update cycle.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
