[CVE-2026-74711][MODERATE REGULAR] hwmon: (pmbus) Fix type confusion in notification logic [ Upstream

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

CVE: CVE-2026-74711
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hwmon: (pmbus) Fix type confusion in notification logic [ Upstream
Commit: 821f6416e69782fa662aff94b5ea52c943042790
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=821f6416e69782fa662aff94b5ea52c943042790
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74711
Analysis date: Sat, 22 Aug 2026 17:39:34 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline manual review required. Not Strong Important by current evidence
Manual review required: YES

Summary:
A type confusion in the PMBus hwmon notification path can cause `pmbus_notify()` to read an `index` field from the wrong attribute container, creating a slab OOB read candidate and possible incorrect notification matching, but no direct network trigger or strong privilege-escalation primitive is demonstrated.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74711 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74711

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: YES

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-2026-74711	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-843;CWE-125;CWE-704;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.8';DESCR 'A type confusion in the PMBus hwmon notification path can occur because pmbus_notify casts every attribute in data group attrs to sensor_device_attribute and then reads attr index. Some entries are backed by other PMBus attribute containers, so the index read can become a slab out-of-bounds read or can overlap unrelated page phase and register fields and cause incorrect notification matching. For the CVSS the PR:L is used because reliable triggering normally requires local access to a system with a PMBus hwmon device and the ability to influence the local device or notification path, but full administrative privileges are not necessarily a safe assumption for all deployments. The issue is not network reachable. Impact is at least local denial of service or incorrect hwmon notification behavior, and in the paranoid score may allow limited confidentiality or integrity impact due to kernel memory out-of-bounds read semantics and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review required. Not Strong Important by current evidence (with actual score 4)  SKIP CVE-2026-74711 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	READ OOB INIT HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline manual review required. Not Strong Important by current evidence**

## 2. Signal breakdown

Conservative signals:

* `+1 Firmware-mediated external influence`
  The vulnerable path is in PMBus notification handling and can be reached through device alert or notification activity rather than a normal remote network interface.

* `+1 Memory corruption, weak/indirect corruption candidate`
  The patch fixes type confusion between `device_attribute` and `sensor_device_attribute`. For `pmbus_samples_reg`, the old cast could read `attr->index` past the end of the allocated object, which is a slab OOB read candidate.

* `+1 Privileged kernel/device-management memory corruption path`
  The bug is in a hardware monitoring driver notification path fed by device state or alerts. Attacker control is weak, but the invalid object interpretation occurs in trusted kernel driver code.

Paranoid additional signal:

* `+1 Weak LPE concern`
  This is not a proven privilege-escalation primitive, but type confusion plus kernel OOB read and bogus object interpretation justifies manual review. There is no demonstrated reclaim, overwrite, callback control, or refcount takeover, so this is not a strong LPE signal.

Not awarded:

* No `Remote reachable / network-triggerable` signal. This is not a network protocol parser or packet path.
* No `Strong corruption primitive`. The patch shows invalid read/type confusion, not OOB write, UAF reclaim, arbitrary write, or controlled overwrite.
* No strong confidentiality signal. The OOB value is not shown to be returned to userspace.
* No strong integrity signal. Spurious notification matching is possible, but no protected data modification is shown.
* No reliable strong DoS signal. The commit says the OOB read might trigger a slab OOB read, but does not show a reliable production crash.

## 3. Reachability analysis

The bug is reachable only on systems with PMBus hwmon support and affected PMBus attributes registered. Triggering appears tied to the PMBus alert or notification path, so practical attacker influence depends on local access to the device environment, firmware/device behavior, or ability to induce PMBus events.

A normal remote network attacker cannot trigger this directly. A local unprivileged user may not reliably trigger the notification path on typical systems, but full root should not be assumed in all deployments because hwmon devices and alert behavior can be exposed through platform-specific management stacks.

Namespaces and containers usually do not make PMBus hardware directly reachable unless device nodes, sysfs, or management interfaces are delegated. Call-site confidence: high, because the relevant notification loop and affected attribute containers are present in the patch.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate than an Important-class issue. The technical class is type confusion with a slab OOB read candidate, so it should not be auto-closed without review. However, the realistic exploitation evidence is limited: there is no write primitive, no UAF, no callback hijack, no direct disclosure path, and no network reachability.

Theoretical memory-corruption concern exists because the kernel reads an `index` field through the wrong enclosing type. Realistically, the most supported impacts are incorrect hwmon notification matching, possible warning/crash under hardened/debug conditions, or limited local DoS.

## 5. One-sentence report phrase

A type confusion in the PMBus hwmon notification path can cause `pmbus_notify()` to read an `index` field from the wrong attribute container, creating a slab OOB read candidate and possible incorrect notification matching, but no direct network trigger or strong privilege-escalation primitive is demonstrated.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is kernel type confusion with a slab OOB read candidate. Even though the current evidence does not support Important severity, the bug class is risky enough that it should not be automatically closed as an ordinary low-risk Moderate.

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

Patch: hwmon: (pmbus) Fix type confusion in notification logic [ Upstream
Commit: 821f6416e69782fa662aff94b5ea52c943042790
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=821f6416e69782fa662aff94b5ea52c943042790

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=821f6416e69782fa662aff94b5ea52c943042790

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

The original Linux kernel CVE announcement for CVE-2026-74711 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74711

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:H/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 3
  Paranoid ActionableScore: 4

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).