CVE-2026-31486
Received Received - Intake
Race Condition in Linux Kernel PMBus Regulator Operations

Publication date: 2026-04-22

Last updated on: 2026-06-01

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: hwmon: (pmbus/core) Protect regulator operations with mutex The regulator operations pmbus_regulator_get_voltage(), pmbus_regulator_set_voltage(), and pmbus_regulator_list_voltage() access PMBus registers and shared data but were not protected by the update_lock mutex. This could lead to race conditions. However, adding mutex protection directly to these functions causes a deadlock because pmbus_regulator_notify() (which calls regulator_notifier_call_chain()) is often called with the mutex already held (e.g., from pmbus_fault_handler()). If a regulator callback then calls one of the now-protected voltage functions, it will attempt to acquire the same mutex. Rework pmbus_regulator_notify() to utilize a worker function to send notifications outside of the mutex protection. Events are stored as atomics in a per-page bitmask and processed by the worker. Initialize the worker and its associated data during regulator registration, and ensure it is cancelled on device removal using devm_add_action_or_reset(). While at it, remove the unnecessary include of linux/of.h.
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Meta Information
Published
2026-04-22
Last Modified
2026-06-01
Generated
2026-06-16
AI Q&A
2026-04-22
EPSS Evaluated
2026-06-15
NVD
CVE-2026-31486
EUVD
EUVD-2026-24852
Affected Vendors & Products
Showing 10 associated CPEs
Vendor Product Version / Range
linux linux_kernel 3.19
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel From 6.19 (inc) to 6.19.11 (exc)
linux linux_kernel From 3.19.1 (inc) to 6.18.21 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-667 The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
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Executive Summary

This vulnerability exists in the Linux kernel's hardware monitoring (hwmon) subsystem, specifically in the pmbus/core regulator operations. Certain functions that access PMBus registers and shared data—namely pmbus_regulator_get_voltage(), pmbus_regulator_set_voltage(), and pmbus_regulator_list_voltage()—were not protected by a mutex, which could lead to race conditions.

However, simply adding mutex protection caused deadlocks because the notification function pmbus_regulator_notify() is often called with the mutex already held. If a regulator callback then calls one of the voltage functions, it tries to acquire the same mutex again, causing a deadlock.

The fix involved reworking pmbus_regulator_notify() to use a worker function that sends notifications outside the mutex protection. Events are stored atomically and processed asynchronously, preventing deadlocks while maintaining thread safety.

Impact Analysis

This vulnerability can lead to race conditions in the Linux kernel's hardware monitoring subsystem, which may cause unpredictable behavior or system instability.

Additionally, attempts to fix the issue by adding mutex protection without proper design could cause deadlocks, potentially freezing parts of the system or causing crashes.

Overall, the impact could be system reliability issues, especially in environments relying on accurate hardware monitoring and regulation.

Mitigation Strategies

To mitigate this vulnerability, update the Linux kernel to a version that includes the fix for the pmbus regulator operations race condition.

The fix involves reworking pmbus_regulator_notify() to use a worker function for notifications outside mutex protection, preventing deadlocks.

Ensure that the kernel you use has this patch applied to protect regulator operations with mutex and avoid race conditions.

Compliance Impact

The provided information does not specify any impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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