[CVE-2026-98000][MODERATE REGULAR] hwmon: Fix potential UAF in pec_store [ Upstream

[CVE-2026-98000][MODERATE REGULAR] hwmon: Fix potential UAF in pec_store [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98000
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: hwmon: Fix potential UAF in pec_store [ Upstream
Commit: 8afab57bcdbc2186f325972e777880ac5a220f4f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8afab57bcdbc2186f325972e777880ac5a220f4f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98000
Analysis date: Sat, 26 Sep 2026 03:04:41 -0400
ActionableScore: 3
ActionableScore lower bound: unknown
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98000 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98000

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-98000	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98000 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:H/I:H/A:H';*CWE-416;*CWE-672;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A use-after-free can occur in pec_store() because guard based mutex cleanup runs only when the function returns. If the chip write callback reports an error and put_device() drops the final reference, the hwmon device and its embedded mutex may be freed before the cleanup code calls mutex_unlock(). The resulting unlock operates on freed memory and may cause a kernel crash or corrupt memory if the allocation is reused. For the CVSS the PR:L reflects environments where write access to the hwmon PEC sysfs attribute is delegated to a restricted service account or container root without full system privileges. Typical systems restrict this interface to an administrator, which would instead support PR:H. AC:H applies because triggering depends on a qualifying driver error, final reference release, and favorable object lifetime conditions. The issue is local and is not directly reachable through network traffic. Impact is at least a local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to memory corruption and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)  SKIP CVE-2026-98000 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	UAF HARDWARE  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	-	-	checked

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

ActionableScore=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Positive signals:

* +2 Real UAF. `put_device(hdev)` may drop the final reference and free `hwdev`, after which automatic guard cleanup calls `mutex_unlock()` on the freed embedded mutex.
* +1 Realistic kernel crash or strong DoS. Unlocking a freed mutex can produce KASAN reports, an Oops, or kernel-state corruption sufficient to crash the system.

Negative signals:

* None. No privilege, race, hardware-rarity, or subsystem penalty is justified by the supplied evidence.

Material signals not awarded:

* No controlled reclaim or attacker-shaped replacement object is demonstrated.
* No arbitrary or directed kernel write is demonstrated. `mutex_unlock()` performs a fixed operation on the stale mutex rather than an attacker-selected write.
* No structured stale-object leverage is awarded because the stale operation is limited to guard cleanup of the embedded mutex.
* No Weak or Strong LPE point is awarded merely from the UAF or theoretical allocator reuse.
* No concrete repeated release/refcount point is awarded. `put_device()` is the only lifetime operation. The later `mutex_unlock()` mutates mutex state but is not a second release, put, free, or refcount mutation.
* No paranoid repeated-refcount point applies.
* FLOOR 5 does not apply because there is no second lifetime mutation, controlled reclaim, or meaningful post-reuse structured processing.
* No extra Availability point is awarded for the same possible crash.
* Confidentiality and integrity points are not awarded because no disclosure, attacker-directed corruption, or security-boundary effect is established.
* Remote reachability is not established.

3. Reachability analysis

The trigger requires writing the hwmon PEC sysfs attribute, receiving an error other than `-EOPNOTSUPP` from the chip write callback, and having `put_device()` release the final device reference.

The supplied patch does not show the attribute mode, ownership, delegated permissions, or complete device-removal sequence. Standard sysfs deployment may restrict this operation to an administrator, but the provided evidence does not positively establish host-admin-equivalent privilege for every affected configuration. Therefore, `HostAdminRequired=UNKNOWN`.

No evidence shows that the complete operation is available through attacker-created user or network namespaces, so `NamespaceScopedPrivilege=UNKNOWN`. The path requires a registered hwmon device and driver exposing PEC control, but hardware-specific code alone does not justify a rarity penalty.

This is an ordered error-path lifetime failure, not a demonstrated timing race. The final-reference condition may depend on concurrent device teardown, but the evidence does not establish either a reliably attacker-controlled race or a sufficiently narrow race for a timing penalty.

4. Primitive and severity interpretation

The exact primitive is a post-lifetime `mutex_unlock()` against a mutex embedded in a potentially freed `hwmon_device`. This is a real UAF and therefore CLASS_B.

The stale object is structurally active, but the demonstrated stale use is narrow and cleanup-oriented. It does not consume attacker-controlled pointers, callbacks, lengths, ownership fields, or replacement-object state. The first lifetime operation, `put_device()`, may destroy the object. However, the subsequent operation is mutex cleanup rather than a second lifetime or refcount mutation.

The demonstrated consequence is invalid access to freed mutex storage with plausible kernel crash or corruption. Privilege escalation remains theoretical because no controlled reclaim, useful replacement type, callback influence, disclosure, or directed write is established.

`ImportantCandidate=NO` because the evidence supports a constrained cleanup UAF rather than an unresolved exploitation primitive with meaningful reuse leverage. `AutoDowngradeAllowed=YES` because the established result is primarily crash/DoS, with no repeated release, authorization bypass, controlled corruption, or security-boundary primitive.

5. One-sentence report phrase

A final `put_device()` in `pec_store()` can free the hwmon device before automatic guard cleanup unlocks its embedded mutex, causing a local cleanup-path use-after-free and possible kernel crash.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Confirm the PEC sysfs permissions and whether device removal or another reachable path lets a below-host-admin actor reliably cause the final-reference condition or influence allocation reuse.

7. Call-site confidence

Call-site confidence: high

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

Patch: hwmon: Fix potential UAF in pec_store [ Upstream
Commit: 8afab57bcdbc2186f325972e777880ac5a220f4f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8afab57bcdbc2186f325972e777880ac5a220f4f

Changed files:
  drivers/hwmon/hwmon.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=8afab57bcdbc2186f325972e777880ac5a220f4f

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

The original Linux kernel CVE announcement for CVE-2026-98000 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98000

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