CVE-2026-21019 Overview
CVE-2026-21019 is an improper input validation vulnerability in the FacAtFunction component of Samsung Galaxy Watch. The flaw exists in firmware versions prior to the SMR May-2026 Release 1 security maintenance release. A local attacker can exploit the vulnerability to execute arbitrary code with system privilege on the affected wearable device. Samsung addressed the issue in its May 2026 mobile security bulletin.
Critical Impact
Local attackers can execute arbitrary code with system-level privileges on Galaxy Watch devices, enabling full device compromise and access to sensitive health, location, and authentication data.
Affected Products
- Samsung Galaxy Watch firmware prior to SMR May-2026 Release 1
- Devices receiving the Samsung Mobile Release (SMR) update channel
- Wearables running affected versions of the FacAtFunction service
Discovery Timeline
- 2026-05-13 - CVE-2026-21019 published to NVD
- 2026-05-13 - Last updated in NVD database
- May 2026 - Samsung releases SMR May-2026 Release 1 security patch
Technical Details for CVE-2026-21019
Vulnerability Analysis
The vulnerability resides in FacAtFunction, a factory AT command handler on Galaxy Watch firmware. The handler fails to properly validate input parameters before processing them. An attacker with local access to the device can supply crafted input that bypasses validation logic. Successful exploitation results in arbitrary code execution under the system user context.
System-level execution on a Galaxy Watch grants access to telephony interfaces, sensor data, health records, and paired-phone communication channels. The attack requires no user interaction and no authentication once local access to the AT command interface is achieved.
Root Cause
The root cause is missing or insufficient input validation in the FacAtFunction factory-mode AT command processing routine. Factory AT command handlers are typically exposed for manufacturing and diagnostic purposes and operate with elevated privileges. When such handlers accept attacker-controlled input without sanitization, the resulting memory corruption or command parsing failure can be redirected into code execution.
Attack Vector
The attack vector is local. An attacker must have local access to the Galaxy Watch, which can be obtained through a physical USB or debug connection, a malicious companion application with sufficient permissions, or chained exploitation from another vulnerability that exposes the AT interface. Once positioned, the attacker sends a malformed AT command sequence to FacAtFunction to trigger arbitrary code execution at the system privilege level.
No public proof-of-concept or exploit code is available for this issue. Refer to the Samsung Mobile Security Update for technical details.
Detection Methods for CVE-2026-21019
Indicators of Compromise
- Unexpected factory AT command traffic directed at paired Galaxy Watch devices
- Galaxy Watch processes executing with system privileges outside of normal firmware activity
- Companion mobile applications requesting unusual diagnostic or debug permissions
- Unsigned or unexpected binaries persisting across reboots on the watch
Detection Strategies
- Inventory all Galaxy Watch devices in the environment and verify firmware build against the SMR May-2026 Release 1 baseline
- Monitor mobile device management (MDM) telemetry for wearables reporting outdated security patch levels
- Audit paired companion applications for elevated Bluetooth or USB debugging permissions that could reach the AT interface
Monitoring Recommendations
- Enable security patch level reporting through enterprise mobility management for all wearable endpoints
- Track Samsung Knox attestation results to identify devices that fail integrity checks after potential compromise
- Alert on Galaxy Watch devices that remain unpatched more than 30 days after the May 2026 SMR release
How to Mitigate CVE-2026-21019
Immediate Actions Required
- Apply the SMR May-2026 Release 1 update to all Galaxy Watch devices through the Samsung Wearable companion application
- Restrict physical access to Galaxy Watch devices used in sensitive roles until patching is verified
- Remove or restrict companion applications that request developer mode or factory diagnostic permissions
- Validate firmware version compliance through mobile device management before granting access to corporate resources
Patch Information
Samsung released the fix in the SMR May-2026 Release 1 maintenance update. The patch corrects input validation logic in FacAtFunction so that malformed factory AT commands are rejected before reaching privileged code paths. Patch details and rollout information are published in the Samsung Mobile Security Update bulletin for May 2026.
Workarounds
- Disable USB debugging and developer mode on Galaxy Watch devices that cannot be immediately patched
- Prevent installation of untrusted companion applications that could access factory or AT interfaces
- Enforce device passcode and lock screen policies to limit opportunities for physical access exploitation
# Example: Verify Galaxy Watch security patch level via ADB over Wear
adb shell getprop ro.build.version.security_patch
# Expected value: 2026-05-01 or later (SMR May-2026 Release 1)
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
