CVE-2026-31688: Linux Kernel Race Condition Vulnerability

CVE-2026-31688 Overview

A race condition vulnerability has been identified in the Linux kernel's driver core subsystem related to the driver_match_device() function. The vulnerability stems from inconsistent device lock handling across different call sites, where driver_match_device() is called from three locations but only one (__device_attach_driver) properly holds the device_lock(dev). The other two call sites (bind_store and __driver_attach) do not acquire the lock, creating a race condition that can lead to a use-after-free (UAF) condition.

Critical Impact
This vulnerability allows for use-after-free conditions in the Linux kernel driver core, potentially enabling local privilege escalation or denial of service on affected systems.

Affected Products

Linux kernel (versions utilizing the vulnerable driver core implementation)
Systems with device drivers using the driver_override field
Buses implementing the affected match() callback pattern

Discovery Timeline

2026-04-27 - CVE CVE-2026-31688 published to NVD
2026-04-27 - Last updated in NVD database

Technical Details for CVE-2026-31688

Vulnerability Analysis

The vulnerability exists in the Linux kernel's driver core device matching mechanism. The driver_match_device() function is invoked from three distinct code paths within the kernel, but the locking semantics are inconsistent across these paths. While __device_attach_driver correctly acquires device_lock(dev) before calling the match function, both bind_store() and __driver_attach() fail to hold this lock.

This inconsistency means that bus match() callbacks are not guaranteed to execute with the device lock held, violating expected synchronization guarantees. The driver_override implementation specifically relies on the device lock for safe access to shared data structures. When the lock is not held, concurrent access can result in a use-after-free condition where memory is accessed after being freed by another thread.

Root Cause

The root cause is a locking inconsistency in the kernel's device driver matching subsystem. The driver_match_device() function lacks uniform synchronization guarantees because not all callers acquire the necessary device lock before invocation. This architectural oversight allows race conditions to occur when the driver_override field is accessed concurrently, as this field's implementation assumes the device lock is always held during match operations.

Attack Vector

The attack vector involves triggering concurrent operations through the bind_store() sysfs interface or the __driver_attach() kernel path while simultaneously manipulating device state. An attacker with local access to the system could exploit the race window between the time-of-check and time-of-use of device structures, potentially leading to arbitrary memory access or kernel code execution through the use-after-free condition.

The vulnerability requires local access to interact with the affected sysfs interfaces or trigger driver attachment operations. Exploitation complexity is elevated due to the timing-dependent nature of race conditions.

Detection Methods for CVE-2026-31688

Indicators of Compromise

Unexpected kernel panics or oops messages referencing driver core functions such as driver_match_device, bind_store, or __driver_attach
Memory corruption warnings in kernel logs related to device driver operations
System instability when frequently binding/unbinding device drivers

Detection Strategies

Enable CONFIG_PROVE_LOCKING and CONFIG_LOCKDEP kernel configuration options to detect locking violations
Monitor kernel logs for use-after-free warnings from KASAN (Kernel Address Sanitizer) if enabled
Deploy kernel tracing on driver_match_device() and related functions to identify suspicious call patterns

Monitoring Recommendations

Implement continuous monitoring of kernel log messages for UAF or locking-related warnings
Set up alerts for unexpected kernel crashes or restarts that may indicate exploitation attempts
Review system activity logs for unusual device driver binding/unbinding operations

How to Mitigate CVE-2026-31688

Immediate Actions Required

Update to a patched Linux kernel version containing the fix
Restrict local access to systems running vulnerable kernel versions
Limit user access to sysfs driver binding interfaces where possible
Consider enabling kernel hardening options such as KASAN for detection of exploitation attempts

Patch Information

The vulnerability has been addressed by introducing driver_match_device_locked(), a new helper function that guarantees the device lock is held using a scoped guard. The patch replaces the unlocked calls in bind_store() and __driver_attach() with this new locked helper and adds a lock assertion to driver_match_device() to enforce the locking guarantee.

The fix is available in the kernel git repository at commit dc23806a7c47ec5f1293aba407fb69519f976ee0. For technical details, refer to the Kernel Git Commit Log.

Workarounds

Restrict access to device driver sysfs interfaces by modifying permissions on /sys/bus/*/drivers/*/bind and /sys/bus/*/drivers/*/unbind
Implement SELinux or AppArmor policies to limit which processes can interact with driver binding interfaces
Reduce exposure by disabling unnecessary device driver modules on affected systems

bash

# Restrict access to driver binding interfaces (temporary mitigation)
chmod 600 /sys/bus/*/drivers/*/bind
chmod 600 /sys/bus/*/drivers/*/unbind