CVE-2026-21003: Samsung Android Auth Bypass Vulnerability

CVE-2026-21003 Overview

CVE-2026-21003 is an improper input validation vulnerability in Samsung Android devices that allows physical attackers to bypass network restrictions. The vulnerability exists in the data handling mechanisms related to network restriction features in Samsung's Android implementation prior to the SMR Apr-2026 Release 1 security patch.

Critical Impact

Physical attackers with device access can bypass configured network restrictions, potentially enabling unauthorized network connectivity and data exfiltration on enterprise-managed or restricted Samsung devices.

Affected Products

• Samsung Android 14.0 (all SMR releases prior to Apr-2026 Release 1)
• Samsung Android 15.0 (all SMR releases prior to Apr-2026 Release 1)
• Samsung Android 16.0 (all SMR releases prior to Apr-2026 Release 1)

Discovery Timeline

• April 13, 2026 - CVE-2026-21003 published to NVD
• April 16, 2026 - Last updated in NVD database

Technical Details for CVE-2026-21003

Vulnerability Analysis

This vulnerability stems from insufficient validation of input data within Samsung's network restriction implementation. Network restrictions are commonly used in enterprise environments, parental controls, and MDM (Mobile Device Management) solutions to limit which networks a device can connect to or what network features are accessible.

The improper input validation allows an attacker with physical access to the device to craft or manipulate specific data inputs that the network restriction subsystem fails to properly sanitize or validate. This results in the security controls being bypassed entirely, granting the attacker access to network functionality that should be restricted.

The physical access requirement limits the attack surface to scenarios where an adversary can directly interact with the device. However, this is particularly concerning for enterprise environments where devices may be stolen, lost, or accessed by malicious insiders. Once network restrictions are bypassed, an attacker could potentially connect to unauthorized networks, exfiltrate sensitive data, or download malicious payloads.

Root Cause

The root cause is improper input validation (CWE category) in the network restriction data handling logic. Samsung's implementation fails to adequately validate or sanitize certain input parameters related to network restriction configurations. When malformed or specially crafted input is provided through the device's physical interface, the validation routines fail to reject the invalid data, allowing the restriction bypass to occur.

Attack Vector

Exploitation of this vulnerability requires physical access to the target Samsung Android device. An attacker must be able to directly interact with the device to provide the malicious input that triggers the validation bypass. The attack does not require any special privileges or user interaction beyond physical device access.

The exploitation scenario typically involves:

1. Physical access to a Samsung Android device with network restrictions configured
2. Interaction with device interfaces to provide crafted input data to the network restriction subsystem
3. Successful bypass of network restriction validation checks
4. Unrestricted access to previously blocked network features or connections

Since no verified code examples are available for this vulnerability, readers should refer to the Samsung Security Update for additional technical details regarding the specific vulnerable components and patch implementation.

Detection Methods for CVE-2026-21003

Indicators of Compromise

• Unexpected network connections from devices that have network restrictions configured
• Changes to network restriction policy configurations without authorized administrative action
• Device logs showing network activity to blocked destinations or networks
• MDM alerts indicating policy violations or restriction overrides on managed Samsung devices

Detection Strategies

• Monitor MDM dashboards for devices reporting network restriction policy violations or unexpected network connectivity
• Implement network traffic analysis to detect Samsung devices connecting to unauthorized networks
• Review device audit logs for suspicious configuration changes or anomalous network-related events
• Enable security logging on Samsung Knox-managed devices to capture detailed network restriction events

Monitoring Recommendations

• Configure SIEM rules to correlate Samsung device network activity against configured restriction policies
• Implement alerting for any network restriction policy modifications on enterprise-managed devices
• Monitor for devices that suddenly regain network access after being placed in restricted mode
• Establish baseline network behavior for restricted devices and alert on deviations

How to Mitigate CVE-2026-21003

Immediate Actions Required

• Update all affected Samsung Android devices to SMR Apr-2026 Release 1 or later immediately
• Audit physical security controls for devices with sensitive network restriction configurations
• Review device logs for any signs of prior exploitation attempts or unauthorized network access
• Implement enhanced physical device security measures for enterprise-managed Samsung devices

Patch Information

Samsung has addressed this vulnerability in the SMR Apr-2026 Release 1 security maintenance release. The patch is available through Samsung's standard device update mechanisms. Organizations should prioritize deployment to all Samsung Android devices running versions 14.0, 15.0, and 16.0 with any prior SMR release.

For detailed patch information and update instructions, refer to the Samsung Mobile Security Advisory.

Workarounds

• Implement strict physical access controls to prevent unauthorized physical device access
• Use Samsung Knox device lock features to prevent unauthorized device manipulation
• Consider geofencing or additional location-based policies for high-security devices
• Enable device encryption and strong authentication to limit physical attack effectiveness

# Samsung Knox MDM Policy Verification
# Check device security patch level via ADB
adb shell getprop ro.build.version.security_patch

# Expected output for patched devices: 2026-04-01 or later
# Devices showing earlier dates require immediate update