CVE-2026-23071: Linux Kernel Race Condition Vulnerability

CVE-2026-23071 Overview

A race condition vulnerability has been identified in the Linux kernel's regmap subsystem, specifically within the hwspinlock irqsave routine. The vulnerability exists because the address of a shared member (&map->spinlock_flags) was passed directly to hwspin_lock_timeout_irqsave. This implementation flaw allows multiple contexts contending for the lock to overwrite the shared flags variable, potentially corrupting the state for the current lock owner.

Critical Impact

This race condition could lead to system instability, kernel state corruption, or potential privilege escalation in multi-threaded environments where multiple contexts compete for hardware spinlock resources.

Affected Products

• Linux kernel (multiple stable branches)
• Systems utilizing the regmap hardware spinlock functionality
• Embedded platforms with hardware spinlock dependencies

Discovery Timeline

• 2026-02-04 - CVE CVE-2026-23071 published to NVD
• 2026-02-05 - Last updated in NVD database

Technical Details for CVE-2026-23071

Vulnerability Analysis

The vulnerability resides in the regmap subsystem's implementation of hardware spinlock handling with IRQ save functionality. When acquiring a hardware spinlock with interrupts disabled, the code must preserve the current interrupt state to restore it properly upon lock release. The flawed implementation passed a shared structure member address directly to the lock acquisition function, creating a classic race condition scenario.

In concurrent execution scenarios, when multiple CPU cores or execution contexts attempt to acquire the same hardware spinlock, they would all reference the same memory location for storing IRQ flags. This means that when context A acquires the lock and stores its IRQ state, context B (waiting for the lock) could overwrite that stored state before context A has a chance to restore it upon unlock. This results in incorrect interrupt state restoration, potentially leaving interrupts disabled when they should be enabled, or vice versa.

Root Cause

The root cause is improper synchronization when accessing a shared data structure member (map->spinlock_flags) in a concurrent environment. The design flaw allowed the IRQ flags storage location to be shared across multiple lock contenders rather than being isolated to each execution context. The fix involves using a local stack variable to temporarily store the IRQ state, ensuring each context maintains its own independent copy of the flags.

Attack Vector

While this is primarily a reliability and stability vulnerability, exploitation could occur in scenarios where:

The vulnerability is triggered through normal system operation when multiple kernel subsystems or drivers simultaneously access hardware resources protected by regmap hwspinlocks. An attacker with local access could potentially craft workloads that increase lock contention, amplifying the probability of state corruption. The corrupted interrupt state could lead to system hangs, kernel panics, or in specific scenarios, could be chained with other vulnerabilities for privilege escalation.

Detection Methods for CVE-2026-23071

Indicators of Compromise

• Unexpected system hangs or kernel panics during high I/O operations
• Anomalous interrupt handling behavior or IRQ-related kernel warnings in system logs
• Kernel oops messages referencing regmap or hwspinlock functions
• System instability under concurrent hardware access patterns

Detection Strategies

• Monitor kernel logs (dmesg) for race condition warnings or spinlock-related errors
• Implement kernel debugging tools such as lockdep to detect lock ordering violations
• Use kernel tracing (ftrace) to monitor hwspinlock acquisition patterns
• Deploy SentinelOne Singularity Platform for real-time kernel anomaly detection

Monitoring Recommendations

• Enable kernel lockdep debugging during testing phases to identify potential lock contention issues
• Configure alerting for kernel panic events referencing regmap subsystem components
• Implement system stability monitoring to detect unexpected reboots or hangs
• Review hardware interrupt handling metrics for anomalies in IRQ enable/disable patterns

How to Mitigate CVE-2026-23071

Immediate Actions Required

• Update Linux kernel to patched versions containing the fix
• Review systems with heavy hardware spinlock usage for signs of instability
• Prioritize patching for embedded systems and platforms with hardware spinlock dependencies
• Test kernel updates in staging environments before production deployment

Patch Information

The vulnerability has been resolved in multiple stable kernel branches. The fix uses a local stack variable flags to store the IRQ state temporarily, ensuring isolation between concurrent lock contenders. Patches are available through the following kernel git commits:

• Kernel Git Commit 24f31be
• Kernel Git Commit 4aab0ca
• Kernel Git Commit 4b58aac
• Kernel Git Commit c2d2cf7

Workarounds

• Reduce concurrent access to hardware resources protected by regmap hwspinlocks where possible
• Implement application-level serialization for critical hardware access paths
• Consider disabling non-essential hardware features that rely on hwspinlock during peak workloads
• Monitor system stability closely and restart affected services if anomalies are detected

# Check current kernel version for vulnerability status
uname -r

# View kernel commit history for regmap fixes
git log --oneline drivers/base/regmap/

# Apply kernel updates on Debian/Ubuntu systems
sudo apt update && sudo apt upgrade linux-image-$(uname -r)

# Apply kernel updates on RHEL/CentOS systems
sudo yum update kernel