CVE-2026-72395 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
hwmon: (pmbus) Fix passing events to regulator core
Sashiko reports:
Commit 754bd2b4a084 ("hwmon: (pmbus/core) Protect regulator operations with mutex") introduced a worker to batch regulator events over time using atomic_or(). The delayed worker then passes the combined bitmask unmodified to regulator_notifier_call_chain().
The core regulator subsystem's regulator_handle_critical() function evaluates the event parameter using a strict switch statement. If multiple distinct faults occur before the worker runs (e.g., REGULATOR_EVENT_UNDER_VOLTAGE | REGULATOR_EVENT_OVER_CURRENT), the combined bitmask fails to match any case. This leaves the reason as NULL and completely bypasses the critical hw_protection_trigger().
Fix the problem by passing events bit by bit to the regulator event handler.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability exists within the Linux kernel's hardware monitoring subsystem, specifically in the pmbus driver implementation that interfaces with power management units. The issue stems from a flawed approach to handling multiple simultaneous regulator events that occurred during the introduction of mutex protection for regulator operations in commit 754bd2b4a084. The original implementation attempted to optimize event processing by batching multiple events into a single bitmask using atomic_or() operations within a delayed worker thread before passing this combined event mask to the regulator subsystem's notification chain through regulator_notifier_call_chain(). This approach created a critical failure in the event handling logic where the core regulator subsystem's regulator_handle_critical() function processes events through a strict switch statement that expects individual, distinct event flags rather than combined bitmasks.
The technical flaw manifests when multiple distinct fault conditions occur concurrently before the delayed worker executes, such as REGULATOR_EVENT_UNDER_VOLTAGE and REGULATOR_EVENT_OVER_CURRENT simultaneously. The combined bitmask created by atomic_or() operation fails to match any specific case within the switch statement in regulator_handle_critical(), resulting in a NULL reason parameter being passed to the critical hw_protection_trigger() function. This failure completely bypasses the intended protection mechanisms that should be triggered when critical power delivery conditions occur, leaving the system vulnerable to uncontrolled power delivery failures that could lead to hardware damage or system instability. The vulnerability represents a fundamental misalignment between the event batching approach and the expected interface contract of the regulator subsystem.
The operational impact of this vulnerability is significant as it can result in complete bypassing of critical power protection mechanisms during hardware fault conditions. When multiple power delivery faults occur simultaneously, the system fails to properly trigger protective actions that should be activated immediately upon detection of under-voltage or over-current conditions. This creates a window where potentially damaging power conditions can persist without proper system intervention, potentially leading to hardware corruption, data loss, or even physical damage to components. The vulnerability is particularly concerning in server and embedded systems where reliable power management is critical for system stability and safety, as it essentially disables the automatic protection mechanisms that should be active during fault conditions.
The fix implemented addresses this issue by modifying the event handling approach to process individual events rather than combined bitmasks when communicating with the regulator subsystem. Instead of passing a single combined event bitmask to regulator_notifier_call_chain(), the solution ensures that each distinct event is processed separately and passed individually to the notification chain. This approach aligns with the expected interface requirements of the regulator subsystem's critical handling functions and maintains proper event semantics throughout the power management flow. The fix effectively restores the intended behavior where each individual fault condition triggers appropriate protective actions through the hw_protection_trigger() function, ensuring that system stability and hardware protection are maintained during concurrent power delivery faults.
This vulnerability maps to CWE-391 for unchecked error condition and CWE-755 for improper handling of exceptional conditions within the Linux kernel's power management subsystem. From an ATT&CK perspective, this represents a privilege escalation vector through system instability and potential hardware damage, while also enabling information disclosure through failed protection mechanisms that should have maintained system integrity. The vulnerability demonstrates a classic case where optimization efforts to batch operations inadvertently created security flaws by violating expected interface contracts between kernel subsystems, highlighting the importance of maintaining proper semantic boundaries in kernel development.