CVE-2026-31761: Linux Kernel Race Condition Vulnerability

CVE-2026-31761 Overview

CVE-2026-31761 is a race condition vulnerability in the Linux kernel's Industrial I/O (IIO) gyroscope driver for the InvenSense MPU-3050 sensor. The flaw exists because iio_device_register() was called before the probe function completed device initialization. Userspace can interact with the IIO device through sysfs and character device interfaces as soon as registration occurs. If registration happens before the probe finalizes setup, concurrent access produces a race window with potentially uninitialized state.

The Linux kernel maintainers resolved the issue by relocating iio_device_register() to the end of the probe function and aligning iio_device_unregister() accordingly.

Critical Impact
Local users with access to the gyroscope device can trigger the race window during driver probe to corrupt kernel state, leading to confidentiality, integrity, and availability impact on affected systems.

Affected Products

Linux kernel branches containing the drivers/iio/gyro/mpu3050 driver prior to the fix
Distributions packaging vulnerable stable kernel releases
Embedded and mobile platforms shipping the InvenSense MPU-3050 gyroscope sensor

Discovery Timeline

2026-05-01 - CVE-2026-31761 published to NVD
2026-05-03 - Last updated in NVD database

Technical Details for CVE-2026-31761

Vulnerability Analysis

The Linux IIO subsystem exposes sensor devices to userspace through sysfs entries and character devices. Once iio_device_register() returns, userspace can read attributes, open the device node, and issue ioctls against the driver. The MPU-3050 probe function previously called iio_device_register() before completing initialization steps that the registered interfaces depend on.

This ordering creates a Time-of-Check Time-of-Use (TOCTOU) style race condition. A local process polling the IIO sysfs tree can open the device between registration and full probe completion. The driver may then service requests using state that has not yet been initialized.

The fix moves iio_device_register() to the end of the probe function so registration only occurs after the driver finishes setting up all internal state. The corresponding iio_device_unregister() call is repositioned in the remove path to maintain symmetry.

Root Cause

The root cause is improper ordering of resource registration during driver initialization. Publishing a kernel object to userspace before the object is fully constructed violates initialization invariants and produces a race condition between the probe path and userspace consumers.

Attack Vector

Exploitation requires local access with permissions to interact with IIO device files. An attacker triggers driver loading or rebinding through hot-plug events, module reload, or device unbind/bind via sysfs. The attacker concurrently opens or queries the IIO device to hit the narrow window between registration and probe completion. The resulting impact spans confidentiality, integrity, and availability of kernel memory state, consistent with kernel-level race conditions.

No public proof-of-concept or exploit has been published, and the issue is not listed on the CISA Known Exploited Vulnerabilities catalog. See the upstream commits referenced in kernel.org commit 22487ef85f6d and kernel.org commit caec338f9146 for the corrective patches.

Detection Methods for CVE-2026-31761

Indicators of Compromise

Unexpected kernel oops or warnings referencing mpu3050 or the IIO core during driver probe
Repeated unbind and bind operations against /sys/bus/i2c/drivers/mpu3050 from non-administrative workloads
Concurrent file descriptor opens against /dev/iio:device* nodes coinciding with module load events

Detection Strategies

Audit kernel package versions across the fleet to identify hosts running stable branches that predate the upstream fix commits
Monitor dmesg and persistent kernel logs for IIO subsystem warnings, NULL pointer dereferences, or use-after-free traces involving gyroscope drivers
Track udev and kobject uevents for abnormal frequency of device add and remove cycles on systems exposing the MPU-3050

Monitoring Recommendations

Forward kernel ring buffer events into a centralized logging pipeline and alert on probe-time crash signatures
Enable kernel lockdep and KASAN on test systems running affected drivers to surface race conditions before production deployment
Watch for unprivileged processes invoking writes to driver bind and unbind sysfs files, which can be a precursor to race exploitation

How to Mitigate CVE-2026-31761

Immediate Actions Required

Apply the upstream stable kernel updates that include the reordering of iio_device_register() in the MPU-3050 driver
Rebuild and redeploy custom or vendor kernels that carry the drivers/iio/gyro/mpu3050.c source to incorporate the fix
Restrict access to IIO sysfs and /dev/iio:device* nodes to trusted system services using filesystem permissions and Linux capabilities

Patch Information

The vulnerability is fixed by a series of commits across stable kernel branches. Reference patches include kernel commit 051ca43b0e0e, kernel commit 22487ef85f6d, kernel commit 2a4537653d20, kernel commit 4c0579944910, kernel commit 59a317f82156, kernel commit 92f18aa86302, kernel commit caec338f9146, and kernel commit cc3de12a5612. Coordinate with your distribution vendor to obtain the corresponding backported package release.

Workarounds

Blacklist the mpu3050 kernel module on systems that do not require gyroscope functionality by adding blacklist mpu3050 to a file under /etc/modprobe.d/
Tighten permissions on /sys/bus/i2c/drivers/mpu3050/bind and unbind to prevent unprivileged processes from triggering probe sequences
Apply mandatory access control profiles such as SELinux or AppArmor to confine processes that interact with IIO device nodes

bash

# Blacklist the vulnerable driver until the kernel patch is deployed
echo "blacklist mpu3050" | sudo tee /etc/modprobe.d/disable-mpu3050.conf
sudo rmmod mpu3050 2>/dev/null || true
sudo update-initramfs -u