[CVE-2026-72397][MODERATE REGULAR] hwmon: (pmbus/core) honor vrm_version in pmbus_data2reg_vid() [ Upstream

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

CVE: CVE-2026-72397
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hwmon: (pmbus/core) honor vrm_version in pmbus_data2reg_vid() [ Upstream
Commit: 5bd0d47640395f8a8c34446b62d1781b88869dfa
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5bd0d47640395f8a8c34446b62d1781b88869dfa
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72397
Analysis date: Sun, 16 Aug 2026 00:08:11 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline Moderate / manual review for hardware impact
Manual review required: NO

Summary:
pmbus_data2reg_vid used VR11 VID encoding for all voltage writes even when a driver selected another vrm_version, allowing a privileged or delegated local voltage-control actor to send unsafe PMBus voltage commands that may cause device instability, shutdown, or hardware damage.

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

The original Linux kernel CVE announcement for CVE-2026-72397 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72397

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: MODERATE REGULAR
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-2026-72397	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-682;CWE-840;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'pmbus_data2reg_vid used VR11 VID encoding for all PMBus voltage writes even when the driver selected another vrm_version such as VR12, VR13, IMVP9, amd625mv, or nvidia195mv. A local actor able to write the exposed regulator or hwmon voltage setter could request one voltage while the device receives a different VID code, which may overvolt or undervolt hardware and cause instability, shutdown, or hardware damage. For the CVSS the PR:L is used in the paranoid score because some deployments may delegate voltage control to local services or reduced capability operators, although direct sysfs or regulator writes are usually administrative. The issue is not network reachable. Impact is denial of service through unsafe power configuration rather than information disclosure or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline Moderate / manual review for hardware impact (with actual score 2)	YES	 INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline Moderate / manual review for hardware impact**::

## 2. Signal breakdown

Triggered signals:

* Reliable device DoS / strong availability concern: +1
  Wrong PMBus VID encoding can overvolt or undervolt the device, causing instability, shutdown, or possible hardware damage.

* Availability impact realistic: +1
  The impact may go beyond a transient kernel warning because incorrect voltage commands can affect actual hardware state.

* Practical exploit chain strongly implied: +1
  Local voltage write -> wrong VID conversion -> PMBUS_VOUT_COMMAND receives incorrect code -> hardware receives unsafe voltage.

* Local reduced-privilege trigger in paranoid interpretation: +1
  Some systems may delegate regulator or hwmon voltage control to local services, operators, or reduced capability environments.

Subtracted signals:

* Requires admin/root or equivalent in typical deployments: -2 conservative
  Direct hwmon/regulator voltage writes are normally restricted to privileged users.

* Hardware-specific exposure: -1 paranoid
  The issue only matters on PMBus devices using non-VR11 VID modes and exposing writable voltage controls.

Not triggered:

* No generic memory corruption.
* No UAF, OOB write, double free, refcount bug, or type confusion.
* No network reachability.
* No confidentiality or integrity impact in the kernel security sense.
* No privilege escalation primitive supported by the patch.

## 3. Reachability analysis

The realistic trigger is a local actor able to write a regulator or hwmon voltage setter for an affected PMBus device. In typical deployments this requires administrator privileges or a privileged management daemon, so the conservative score applies the admin privilege penalty. In some embedded, appliance, lab, or fleet-management deployments, voltage control may be delegated to a reduced-privilege local service or operator role, which justifies the paranoid lower-privilege interpretation.

Namespaces and containers do not normally make this reachable unless the relevant sysfs/regulator interface or device-management service is exposed into the container. The path is not remotely reachable by packet traffic. The affected configuration is hardware-dependent and requires a non-VR11 VID mode such as VR12, VR13, IMVP9, amd625mv, or nvidia195mv.

Call-site confidence: medium. The changed helper is clearly used for PMBus voltage write conversion, but the full set of write call sites and product-specific permissions are not included in the patch.

## 4. Severity interpretation

This behaves like a hardware-specific Moderate issue, not an Important-class kernel memory corruption bug. The realistic impact is unsafe power configuration causing device instability, shutdown, or hardware damage. There is no evidence of kernel memory corruption, information disclosure, privilege escalation, or remote triggering.

The paranoid score is higher because the patch context directly shows dangerous voltage misencoding and because real-world impact depends on hardware behavior and permission delegation. It should not be auto-closed purely as a harmless correctness fix, but it also does not reach Actionable Moderate or Important under the provided scoring rules.

## 5. One-sentence report phrase

pmbus_data2reg_vid used VR11 VID encoding for all voltage writes even when a driver selected another vrm_version, allowing a privileged or delegated local voltage-control actor to send unsafe PMBus voltage commands that may cause device instability, shutdown, or hardware damage.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the practical severity depends on affected PMBus hardware, whether writable voltage controls are exposed, and whether voltage management is delegated to reduced-privilege services.

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

Patch: hwmon: (pmbus/core) honor vrm_version in pmbus_data2reg_vid() [ Upstream
Commit: 5bd0d47640395f8a8c34446b62d1781b88869dfa
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5bd0d47640395f8a8c34446b62d1781b88869dfa

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=5bd0d47640395f8a8c34446b62d1781b88869dfa

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

The original Linux kernel CVE announcement for CVE-2026-72397 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72397

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:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 3

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: MODERATE
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).