[CVE-2026-72395][LOW] hwmon: (pmbus) Fix passing events to regulator core [ Upstream

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-72395
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: hwmon: (pmbus) Fix passing events to regulator core [ Upstream
Commit: 2106bf4056858fcce3624e0c51f6fee4d41d3f2f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2106bf4056858fcce3624e0c51f6fee4d41d3f2f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72395
Analysis date: Sun, 16 Aug 2026 02:23:39 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A PMBus regulator event batching bug can pass combined fault bitmasks to the regulator core, causing critical events such as under voltage plus over current to be ignored and potentially bypassing hardware protection handling on affected systems.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-72395 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72395

The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.

The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.

Published priority for this report: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-72395	LOW	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-703;CWE-754;CWE-693;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A logic error in the PMBus regulator event path can cause multiple regulator faults to be merged into one combined bitmask before being passed to the regulator core. The regulator critical handler expects a single event value and uses strict event matching, so a combined event such as under voltage plus over current may not match any critical case and can bypass the hardware protection trigger. For the CVSS the PR:L is used only for the paranoid local scenario where a low privileged local actor can influence PMBus or regulator fault conditions through delegated hardware management access. The issue is not network reachable and does not provide a memory corruption primitive. Impact is denial of service or hardware protection bypass on affected systems, with no evidence of confidentiality impact or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	SIMPLEFIX  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1
  PMBus regulator fault events are driven by hardware, firmware, or electrical fault conditions, but this is not directly network reachable.
* Availability impact realistic: +1
  Bypassing `hw_protection_trigger()` can prevent expected critical protection handling and may lead to system instability or hardware-related DoS on affected platforms.
* Rare AND difficult-to-reach subsystem/configuration: -1
  This requires PMBus hardware, regulator integration, fault-injection-like conditions, and multiple distinct regulator events being batched before the worker runs.

Paranoid additional signal:

* Local low-privileged trigger in special deployments: +1
  Only applies if a local low-privileged actor can indirectly influence PMBus/regulator fault conditions through delegated hardware management, testing, or monitoring interfaces.

Not applied:

* No generic memory corruption.
  The patch fixes event dispatch semantics, not UAF, OOB, double-free, type confusion, or arbitrary write.
* No privilege escalation plausible.
  There is no supported LPE primitive.
* No confidentiality or integrity impact.
  The issue is a hardware protection bypass and availability concern, not data exposure or memory corruption.
* No remote reachable signal.
  The affected path is local hardware/regulator event handling, not a network protocol path.

## 3. Reachability analysis

The bug is triggered when multiple distinct PMBus regulator fault events are ORed together before the delayed worker calls the regulator notifier chain. The regulator core expects a single event value, so the combined bitmask can fail strict switch matching and skip critical protection handling.

Realistic triggering normally requires affected PMBus hardware and actual or induced regulator fault conditions. A normal remote attacker cannot trigger this over the network. A local attacker also usually cannot trigger it unless the system exposes hardware management or fault-control interfaces to non-admin users.

Namespaces and containers generally do not lower privileges here, because PMBus regulator control is not a typical namespace-delegated interface. Call-site confidence: high, because the patch includes the worker call site and the commit explains the downstream regulator handler behavior.

## 4. Severity interpretation

This behaves more like an ordinary Moderate or Low-like hardware-specific availability issue than an Important kernel vulnerability. The practical impact is bypass of critical regulator protection handling, which can matter on platforms that rely on PMBus regulator events for shutdown or protection decisions.

Theoretical risk is limited to system instability, missed hardware protection, or DoS. There is no realistic evidence of memory corruption, privilege escalation, information disclosure, or cross-boundary access.

## 5. One-sentence report phrase

A PMBus regulator event batching bug can pass combined fault bitmasks to the regulator core, causing critical events such as under voltage plus over current to be ignored and potentially bypassing hardware protection handling on affected systems.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

Generic security triage can auto-close or defer this unless the product uses PMBus regulator protection for safety-critical or high-availability hardware. Manual product-specific review is reasonable only for platforms where missed regulator fault handling can cause severe operational impact.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: hwmon: (pmbus) Fix passing events to regulator core [ Upstream
Commit: 2106bf4056858fcce3624e0c51f6fee4d41d3f2f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2106bf4056858fcce3624e0c51f6fee4d41d3f2f

Changed files:
  drivers/hwmon/pmbus/pmbus_core.c

Diff excerpt:

Not included in this email. See the upstream URL for the full patch.

Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2106bf4056858fcce3624e0c51f6fee4d41d3f2f

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-72395 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72395

The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.

The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.

This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.

The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.

Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:

  Conservative CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.

CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.

A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.

  Conservative ActionableScore: 1
  Paranoid ActionableScore: 2

The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.

For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:

  ActionableScore below 5   -> MODERATE REGULAR
  ActionableScore 5 or more -> MODERATE 7.0

The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.

There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).

KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.

AL-KERNEL base severity for this report: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).

Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).