CVE-2026-19575: Critical Kernel Privilege Escalation in Zephyr RTOS – What You Need to Know

Introduction

CVE-2026-19575 represents a critical vulnerability in the Zephyr RTOS kernel that enables local unprivileged users to execute arbitrary code in kernel mode. This privilege escalation flaw exploits insufficient type validation in the device_deinit() system call, bypassing user-space isolation boundaries entirely. For organizations deploying Zephyr RTOS in embedded systems, IoT devices, and real-time applications, this vulnerability poses an immediate and severe risk to system integrity and data security.

What is CVE-2026-19575?

Vulnerability Overview

CVE-2026-19575 is a critical kernel privilege escalation vulnerability affecting the Zephyr RTOS operating system. The flaw resides in the user-mode verification handler for the device_deinit() system call, which fails to properly validate kernel object types before processing user-supplied arguments.

The vulnerability allows an unprivileged local thread to:

• Bypass type validation mechanisms
• Pass arbitrary kernel objects to privileged functions
• Execute code with kernel-level privileges
• Achieve complete system compromise

CVSS Score: 9.8 (Critical)
Attack Vector: Local
Complexity: Low
Privileges Required: None

Affected Component: device_deinit() System Call

The vulnerable code exists in the z_vrfy_device_deinit() function within kernel/device.c. This function serves as the user-mode verification handler for device de-initialization operations.

The problematic validation code uses:

K_SYSCALL_OBJ_INIT(dev, K_OBJ_ANY)

This validation approach is designed to check whether a user-mode thread has permission to access a kernel object. However, the use of K_OBJ_ANY as the type parameter creates a critical security gap.

Why KOBJANY Validation Fails

The K_OBJ_ANY type parameter in the validation macro was intended to provide flexibility for generic object handling. Instead, it creates a type confusion vulnerability:

• Insufficient Type Checking: The validator accepts any kernel object type that the calling thread can access, regardless of whether it’s actually a device object
• No Type Enforcement: Unlike specific type checks (e.g., K_OBJ_DEVICE), K_OBJ_ANY performs minimal validation
• Attacker-Controlled Objects: An attacker can pass user-mode writable objects (such as thread stacks or memory buffers) that will pass validation
• Memory Dereferencing: The kernel subsequently dereferences these attacker-controlled objects, leading to arbitrary memory access

Which Systems Are Vulnerable?

Zephyr Versions 4.2.x and 4.3.x

All Zephyr RTOS versions 4.2.x and 4.3.x are vulnerable by default when compiled with standard configurations. These versions include the flawed device_deinit() implementation without protective measures.

Default Vulnerable Configuration:

• CONFIG_USERSPACE=y (user-space isolation enabled)
• CONFIG_DEVICE_DEINIT_SUPPORT=y (device de-initialization support enabled)

Zephyr Version 4.4.x with CONFIGDEVICEDEINIT_SUPPORT Enabled

Zephyr 4.4.x introduced changes to the device management subsystem. However, systems running 4.4.x remain vulnerable if CONFIG_DEVICE_DEINIT_SUPPORT is explicitly enabled during kernel compilation.

Version 4.4.x with CONFIG_DEVICE_DEINIT_SUPPORT=n (disabled) is not vulnerable.

Configuration Requirements for Exposure

The vulnerability requires specific kernel configurations to be exploitable:

Systems with CONFIG_USERSPACE=n (monolithic kernel mode) are not vulnerable, as user-space isolation is not enforced.

How the Exploit Works

Type Validation Bypass Mechanism

The exploitation begins with understanding how the kernel validates system call arguments:

1. User-Mode Call: An unprivileged thread calls device_deinit(dev_ptr) with a crafted pointer
2. Verification Handler Invocation: The kernel’s verification handler z_vrfy_device_deinit() is triggered
3. Type Check Failure: The K_SYSCALL_OBJ_INIT(dev, K_OBJ_ANY) macro accepts the object without proper type validation
4. Validation Bypass: The function returns success despite the object not being a legitimate device structure

Kernel Object Confusion Attack

The attacker exploits type confusion by passing objects that are not device structures:

Attacker-Controlled Object Types:

• Thread stack memory (user-writable)
• Heap-allocated buffers
• Memory-mapped I/O regions
• Other kernel objects with accessible memory

The kernel’s type validator accepts these objects because K_OBJ_ANY performs minimal type enforcement. The subsequent code treats the attacker-controlled memory as if it were a legitimate device structure.

Memory Dereferencing and Arbitrary Code Execution

Once the validation is bypassed, the kernel proceeds to dereference the attacker-controlled object:

// Vulnerable code path (simplified)
struct device *dev = (struct device *)user_supplied_ptr;
dev->api->deinit(dev);  // Arbitrary function pointer dereference

The attacker can:

1. Craft Memory Layout: Place function pointers at specific offsets in user-writable memory
2. Control Dereferencing: The kernel dereferences these attacker-controlled pointers
3. Execute Arbitrary Code: Function pointers direct execution to attacker-supplied code
4. Operate in Kernel Mode: Execution occurs with full kernel privileges

From Local Access to Kernel Compromise

The complete exploitation chain:

1. Initial Access: Attacker gains local user-mode access to the system
2. Vulnerability Trigger: Craft and pass malicious object to device_deinit()
3. Validation Bypass: Type checking fails due to K_OBJ_ANY weakness
4. Code Execution: Arbitrary code executes in kernel mode
5. Privilege Escalation: Attacker gains complete kernel-level control
6. System Compromise: Full access to all system resources and data

Real-World Attack Scenarios

Local Privilege Escalation Attack

Scenario: A developer or contractor with limited user-mode access to an embedded device exploits CVE-2026-19575 to gain kernel-level control.

Attack Steps:

1. Compile a malicious user-mode application with embedded exploit code
2. Deploy the application to the target device
3. Craft a kernel object that passes K_OBJ_ANY validation
4. Call device_deinit() with the malicious object
5. Kernel dereferences attacker-controlled memory
6. Exploit code executes with kernel privileges
7. Attacker disables security features, installs rootkits, or exfiltrates data

Impact: Complete system compromise, unauthorized access to all device functionality and data.

Denial of Service Through Kernel Fault

Scenario: An attacker aims to disrupt device availability rather than gain persistent access.

Attack Steps:

1. Craft an object that causes a supervisor-mode fault when dereferenced
2. Pass the object to device_deinit()
3. Kernel attempts to dereference invalid memory
4. Supervisor-mode fault occurs
5. Kernel panic and system reboot

Impact: Service interruption, loss of availability, potential data loss.

Data Breach and System Compromise Risks

Scenario: An attacker with local access seeks to extract sensitive data from a medical device or industrial control system.

Attack Steps:

1. Exploit CVE-2026-19575 to gain kernel access
2. Disable memory protection mechanisms
3. Read protected memory regions containing encryption keys or sensitive data
4. Modify firmware or configuration to maintain persistence
5. Establish covert communication channel for data exfiltration

Impact: Data breach, regulatory violations, loss of system integrity, potential safety hazards in critical systems.

Severity Assessment

CVSS 9.8 Critical Rating Explained

The CVSS v3.1 score of 9.8 reflects the severe nature of this vulnerability:

Score Calculation: 9.8 (Critical) indicates near-maximum severity.

Why Local Attacks Are High-Impact

Local privilege escalation vulnerabilities are particularly dangerous because:

• Ubiquitous Access: Many systems have multiple local users or processes
• Supply Chain Risk: Third-party applications or firmware updates may contain exploit code
• Persistence: Kernel-level access enables rootkit installation and long-term compromise
• Isolation Bypass: Defeats the primary security boundary in multi-user systems
• Cascading Compromise: Kernel access enables attacks on other systems or data

Threat Level in Production Environments

For production deployments of Zephyr RTOS:

• IoT Devices: Connected devices become entry points for network-wide attacks
• Industrial Control Systems: Compromise can lead to physical safety hazards
• Medical Devices: Patient safety and data privacy are at risk
• Automotive Systems: Vehicle control systems could be compromised
• Smart Home Infrastructure: Home automation systems become attack vectors

How to Identify If You’re Vulnerable

Check Your Zephyr Version

Determine your current Zephyr RTOS version:

# Check version in CMakeLists.txt or prj.conf
grep -i "zephyr" CMakeLists.txt
# Or check the Zephyr installation
west --version

Vulnerable Versions:

• 4.2.0 through 4.2.x (all)
• 4.3.0 through 4.3.x (all)
• 4.4.x (only if CONFIGDEVICEDEINIT_SUPPORT is enabled)

Verify CONFIGDEVICEDEINIT_SUPPORT Status

Check your kernel configuration file:

# Search in prj.conf or build configuration
grep "CONFIG_DEVICE_DEINIT_SUPPORT" prj.conf
# Check in build directory
grep "CONFIG_DEVICE_DEINIT_SUPPORT" build/.config

Vulnerable Configuration:

CONFIG_DEVICE_DEINIT_SUPPORT=y
CONFIG_USERSPACE=y

Safe Configuration:

CONFIG_DEVICE_DEINIT_SUPPORT=n

Review Kernel Configuration Files

Examine your project’s configuration files:

1. prj.conf: Main project configuration
2. boards/: Board-specific configurations
3. build/.config: Generated build configuration
4. CMakeLists.txt: Build system configuration

Look for any explicit enabling of CONFIG_DEVICE_DEINIT_SUPPORT.

Static Code Analysis Approach

Perform static analysis on your kernel build:

# Extract configuration from built kernel
west build -t menuconfig
# Search for vulnerable function in source
grep -r "z_vrfy_device_deinit" zephyr/
# Check for K_OBJ_ANY usage in device handling
grep -r "K_OBJ_ANY" zephyr/kernel/device.c

Immediate Mitigation Steps

Upgrade to Patched Kernel Versions

The most effective mitigation is upgrading to a patched version:

Recommended Actions:

1. For Zephyr 4.2.x Users: Upgrade to Zephyr 4.4.x or later
2. For Zephyr 4.3.x Users: Upgrade to Zephyr 4.4.x or later
3. For Zephyr 4.4.x Users: Ensure CONFIG_DEVICE_DEINIT_SUPPORT=n

Upgrade Process:

# Update Zephyr manifest
west update
# Verify new version
west --version
# Rebuild with patched kernel
west build -b <board> --pristine=always

Disable CONFIGDEVICEDEINIT_SUPPORT

If immediate upgrade is not feasible, disable the vulnerable feature:

Edit prj.conf:

# Disable vulnerable device de-initialization support
CONFIG_DEVICE_DEINIT_SUPPORT=n

Verify Disabled:

west build -t menuconfig
# Navigate to Device Drivers → Device De-initialization Support
# Confirm it is disabled

Important: Verify that your application does not require device de-initialization functionality before disabling this option.

Restrict Local System Access

Implement strict access controls:

• Limit User Accounts: Remove unnecessary local user accounts
• Disable Debug Interfaces: Disable UART/JTAG debug access in production
• Secure Boot: Implement secure boot to prevent unauthorized firmware modification
• Code Signing: Require signed applications and firmware updates
• Access Logging: Enable comprehensive audit logging of system access

Implement Access Control Policies

Deploy security policies to minimize exposure:

# Example access control policy
- Principle of Least Privilege: Grant minimum necessary permissions
- Role-Based Access Control: Assign permissions based on roles
- Multi-Factor Authentication: Require authentication for sensitive operations
- Audit Logging: Log all privileged operations
- Regular Reviews: Periodically review and update access policies

Long-Term Remediation Strategy

Kernel Update Timeline

Establish a systematic update schedule:

Testing Patched Versions

Before production deployment, thoroughly test patched kernels:

1. Functional Testing: Verify all device functionality works correctly
2. Performance Testing: Ensure no performance regressions
3. Security Testing: Validate that the vulnerability is fixed
4. Compatibility Testing: Test with all third-party libraries and drivers
5. Regression Testing: Ensure no new issues are introduced

Testing Checklist:

□ Build patched kernel successfully
□ Boot system and verify basic functionality
□ Test all device drivers and peripherals
□ Run performance benchmarks
□ Execute security test suite
□ Verify no new warnings or errors
□ Document any configuration changes
□ Obtain stakeholder approval for deployment

Monitoring for Exploitation Attempts

Implement continuous monitoring:

• Kernel Log Analysis: Monitor for device de-initialization errors
• Anomaly Detection: Alert on unusual system behavior
• Access Logging: Track all system call invocations
• Performance Monitoring: Detect unexpected CPU or memory usage
• Security Event Correlation: Correlate multiple indicators of compromise

Audit Log Review Procedures

Establish regular audit log review processes:

Review Frequency: Daily for critical systems, Weekly for others
Log Sources:
- Kernel logs (/var/log/kern.log or equivalent)
- System call traces
- Device driver logs
- Security event logs
Review Criteria:
- Unexpected device_deinit() calls
- Supervisor-mode faults
- Memory access violations
- Privilege escalation attempts
- Unusual system behavior

Detection and Monitoring

Kernel Behavior Monitoring

Monitor kernel-level activities for signs of exploitation:

Key Indicators:

• Unexpected calls to device_deinit() from unprivileged contexts
• Supervisor-mode faults or exceptions
• Abnormal memory access patterns
• Unexpected kernel panic or reboot
• Device driver errors or crashes

Monitoring Implementation:

# Enable kernel debugging
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_OPTIMIZATIONS=y
# Enable system call tracing
CONFIG_SYSCALL_TRACING=y
# Monitor kernel logs
dmesg | grep -i "fault\|error\|device"

Unusual Memory Access Patterns

Detect exploitation attempts through memory access analysis:

Suspicious Patterns:

• Rapid sequence of memory allocations followed by de-initialization calls
• Access to memory regions outside normal device structures
• Attempts to dereference user-mode pointers from kernel context
• Modification of kernel data structures from user mode

Detection Methods:

• Memory protection unit (MPU) violations
• Address space layout randomization (ASLR) bypass attempts
• Heap overflow or buffer overflow signatures
• Unauthorized kernel memory access

System Log Analysis for Device Errors

Analyze system logs for exploitation indicators:

Log Patterns to Monitor:

# Device de-initialization errors
"device_deinit: invalid device object"
"device_deinit: type validation failed"
# Memory access violations
"Supervisor fault"
"Memory protection violation"
"Invalid memory access"
# Kernel errors
"Kernel panic"
"Unhandled exception"
"System reset"

Log Analysis Tools:

• Centralized logging (syslog, ELK stack)
• Log aggregation and correlation
• Automated alerting on suspicious patterns
• Historical trend analysis

Runtime Anomaly Detection

Implement runtime monitoring for behavioral anomalies:

Monitored Metrics:

• System call frequency and patterns
• Memory usage and allocation patterns
• CPU utilization and context switching
• Device driver activity and errors
• Interrupt handling and timing

Detection Techniques:

• Baseline establishment and deviation detection
• Machine learning-based anomaly detection
• Statistical analysis of system metrics
• Behavioral profiling of normal operations

Frequently Asked Questions

What is CVE-2026-19575?

CVE-2026-19575 is a critical vulnerability in the Zephyr RTOS kernel that allows unprivileged local users to execute arbitrary code in kernel mode. The flaw exists in the device_deinit() system call’s type validation mechanism, which uses K_OBJ_ANY to validate kernel objects. This overly permissive validation allows attackers to pass arbitrary kernel objects, leading to type confusion and arbitrary code execution with kernel privileges.

How do I know if my system is affected?

Your system is vulnerable if:

1. You’re running Zephyr 4.2.x or 4.3.x with default configuration (both CONFIG_USERSPACE=y and CONFIG_DEVICE_DEINIT_SUPPORT=y)
2. You’re running Zephyr 4.4.x with CONFIG_DEVICE_DEINIT_SUPPORT=y explicitly enabled
3. Your system has local user access (unprivileged users can run applications)

Check your configuration with:

grep "CONFIG_DEVICE_DEINIT_SUPPORT\|CONFIG_USERSPACE" prj.conf build/.config

What’s the immediate action I should take?

Priority Actions:

1. Assess Exposure: Determine if your systems run vulnerable versions
2. Disable Feature: Set CONFIG_DEVICE_DEINIT_SUPPORT=n in prj.conf
3. Restrict Access: Limit local user accounts and debug access
4. Plan Upgrade: Schedule upgrade to patched Zephyr version
5. Monitor: Enable logging and monitoring for exploitation attempts

Can this vulnerability be exploited remotely?

No. CVE-2026-19575 requires local access to the system. An attacker must be able to execute code on the target device to exploit this vulnerability. Remote exploitation is not possible. However, remote attackers could potentially gain local access through other vulnerabilities or supply chain compromises, then exploit CVE-2026-19575 for privilege escalation.

What happens if I disable CONFIGDEVICEDEINIT_SUPPORT?

Disabling CONFIG_DEVICE_DEINIT_SUPPORT eliminates the vulnerability while maintaining normal system functionality for most applications. The device de-initialization feature is not required for standard device driver operation.

Before disabling, verify:

• Your application doesn’t explicitly call device_deinit()
• No custom drivers require device de-initialization
• Device lifecycle management works correctly without this feature

Verification:

# Search for device_deinit usage in your code
grep -r "device_deinit" src/

How can I monitor for exploitation attempts?

Implement multi-layered monitoring:

1. Kernel Logs: Monitor for device de-initialization errors and faults
2. System Calls: Track device_deinit() invocations from unprivileged contexts
3. Memory Access: Alert on supervisor-mode faults and memory violations
4. Performance: Detect unusual CPU or memory usage patterns
5. Audit Logs: Maintain comprehensive logs of system access and privilege changes

Monitoring Command:

# Real-time kernel log monitoring
dmesg -w | grep -i "device\|fault\|error"
# Search historical logs
journalctl -u kernel | grep -i "device_deinit\|supervisor"

References

• CVE-2026-19575 Official Entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-19575
• Zephyr Project Security: https://docs.zephyrproject.org/latest/security/
• Zephyr RTOS Documentation: https://docs.zephyrproject.org/
• Kernel Device Management: https://docs.zephyrproject.org/latest/reference/kernel/device.html
• CVSS v3.1 Specification: https://www.first.org/cvss/v3.1/specification-document
• Zephyr Security Advisories: https://github.com/zephyrproject-rtos/zephyr/security/advisories

Document Version: 1.0
Last Updated: 2024
Classification: Security Advisory
Intended Audience: System Administrators, Security Teams, Embedded Systems Developers