[CVE-2026-74549][MODERATE REGULAR] hwmon: (nct6775-core) Prevent access to unsupported weight registers [ Upstream

[CVE-2026-74549][MODERATE REGULAR] hwmon: (nct6775-core) Prevent access to unsupported weight registers [ Upstream

[AL-KERNEL]

CVE: CVE-2026-74549
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hwmon: (nct6775-core) Prevent access to unsupported weight registers [ Upstream
Commit: 25b528816f5d83be5236dc182692369e8c9402b0
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25b528816f5d83be5236dc182692369e8c9402b0
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74549
Analysis date: Sat, 15 Aug 2026 12:57:35 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review required
Manual review required: YES

Summary:
The nct6775 hwmon driver may read past fixed nct6116 weight-control register arrays and use the resulting garbage values as hardware register addresses, allowing a local trigger on affected hardware to cause invalid hardware access, misconfiguration, or system crash.

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

The original Linux kernel CVE announcement for CVE-2026-74549 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74549

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
======================================================================

CVE-2026-74549	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-125;CWE-129;*CWE-787;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.8';DESCR 'The nct6775 hwmon driver can read past the end of several nct6116 weight control register arrays because the chip exposes up to five PWM channels while these arrays originally contained only three entries. The out of bounds values can then be used as hardware register addresses for later read or write operations, which may cause invalid hardware access, fan control misconfiguration, or a system crash. For the CVSS the PR:L value is used because a local user or local monitoring process may be able to trigger hwmon update paths, while reliable triggering still depends on the affected nct6116 hardware and driver state. The issue is not network reachable. Impact is at least local denial of service or hardware misconfiguration, and in the paranoid interpretation it may allow limited confidentiality or integrity impact due to a kernel global out of bounds read and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review required (with actual score 4)	YES	WRITE KASAN OOB KERNEL_PANIC_PLUS_UAF HARDWARE  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review required**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. hwmon sysfs update paths may be reachable by local users or local monitoring processes, although some control paths may require elevated permissions.
* Memory corruption, weak/indirect corruption candidate: +1. The bug is a global OOB read from fixed register arrays, not an attacker-controlled overwrite.
* Privileged kernel/device-management corruption path: +1. The OOB values are later used as hardware register addresses in a trusted hwmon driver path.
* Integrity impact plausible: +1. Invalid register writes may misconfigure fan/PWM or hardware monitoring state.
* Availability impact realistic: +1. The commit explicitly mentions possible system crashes.
* Corruption primitive constrained: -1. The attacker does not control the OOB payload or target address directly.
* Rare hardware-specific condition: -1. The issue depends on affected nct6116-compatible hardware and specific PWM capability state.

Paranoid additional signal:

* Reliable kernel crash / strong DoS: +1. If invalid register access is reproducible on affected hardware, the practical result can be a system-wide crash or unsafe hardware-control failure.

No remote reachability, no strong LPE primitive, no arbitrary write, no attacker-controlled reclaim, and no demonstrated confidentiality disclosure were identified.

## 3. Reachability analysis

The bug is local and hardware-dependent. It requires a system using the affected nct6775/nct6116 hwmon path where the chip exposes up to five PWM channels while only the first three support weight-control registers. A local user or monitoring daemon may be able to trigger update paths through hwmon sysfs reads or related local activity, while reliable write-oriented triggering may depend on permissions and driver configuration. Containers usually do not expose raw hwmon device control by default, so namespace impact is limited unless the device nodes or sysfs attributes are delegated. The path is not network reachable.

Call-site confidence: medium. The patch and commit identify nct6775_update_pwm as the relevant loop and describe the downstream register read/write use, but the full sysfs caller context is not included.

## 4. Severity interpretation

This is more than an ordinary correctness bug because it includes a kernel global OOB read and later invalid hardware register access. However, it does not show a strong memory corruption primitive, controlled overwrite, type confusion, UAF reclaim, or practical privilege escalation path. Realistic impact is local DoS or hardware misconfiguration on specific systems. Paranoid handling is justified for manual review, but the issue does not look like an Important-class kernel vulnerability based on the supplied patch.

## 5. One-sentence report phrase

The nct6775 hwmon driver may read past fixed nct6116 weight-control register arrays and use the resulting garbage values as hardware register addresses, allowing a local trigger on affected hardware to cause invalid hardware access, misconfiguration, or system crash.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the bug includes an OOB read and invalid hardware register access in a kernel driver, but the primitive is constrained and hardware-specific, so manual review should confirm whether affected product configurations expose the trigger to unprivileged users and whether crashes or unsafe hardware-control effects are reproducible.

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

Patch: hwmon: (nct6775-core) Prevent access to unsupported weight registers [ Upstream
Commit: 25b528816f5d83be5236dc182692369e8c9402b0
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25b528816f5d83be5236dc182692369e8c9402b0

Changed files:
  drivers/hwmon/nct6775-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=25b528816f5d83be5236dc182692369e8c9402b0

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

The original Linux kernel CVE announcement for CVE-2026-74549 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74549

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:L/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).