[CVE-2026-45914][MODERATE REGULAR] Revert "hwmon: (ibmpex) fix use-after-free in high/low store" [ Upstream

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

CVE: CVE-2026-45914
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: Revert "hwmon: (ibmpex) fix use-after-free in high/low store" [ Upstream
Commit: 05112ba67c824ab416cd54307c0b50aba9f0047a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=05112ba67c824ab416cd54307c0b50aba9f0047a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45914
Analysis date: Wed, 27 May 2026 21:41:42 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
A reverted ibmpex teardown ordering change could let a concurrent local hwmon sysfs read race with driver data clearing and trigger a NULL pointer dereference, causing kernel DoS.

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

The original Linux kernel CVE announcement for CVE-2026-45914 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45914

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-2026-45914	MODERATE	CHECK	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-362;**CWE-476;*CWE-416;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'The previous ibmpex change could clear driver data before removing sysfs attributes, creating a teardown race where a concurrent hwmon sysfs read may dereference NULL driver data. A local user may be able to participate by reading exposed hwmon attributes while device removal is in progress, but reliable triggering usually also needs privileged device teardown or a platform removal event. For the CVSS the PR:L is used in the paranoid score because the read side can be available to a local user, although the teardown side is typically privileged or hardware driven. The issue is not network reachable. Impact is denial of service through kernel crash. No supported evidence indicates information disclosure, integrity impact, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2) 	MAYBE	DANGER INIT RACE UAF KERNEL_PANIC_PLUS_UAF HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**::

## 2. Signal breakdown

* Local unprivileged participation: +1 in paranoid scoring
  A local user may be able to read exposed hwmon sysfs attributes while device removal is in progress.

* Reliable kernel crash / strong DoS: +1
  The problematic ordering could allow a sysfs callback to see NULL driver data and dereference it, causing a kernel crash.

* Availability impact realistic: +1
  The supported impact is local DoS through NULL pointer dereference during teardown.

* Hard race / special timing required: -1
  Triggering requires a race between sysfs access and ibmpex device deletion.

* Requires privileged or hardware-driven teardown in typical deployments: -2 conservative
  Reliable triggering usually requires device removal, driver teardown, IPMI/platform events, or administrative control.

* Rare subsystem / hardware-specific path: -1 conservative
  ibmpex is a specific hwmon/IPMI platform driver, not a broad default local API.

* Possible lifetime issue, but not proven exploitable UAF: +0
  The reverted commit was related to an alleged UAF fix, but the patch text says the original race is not proven and the immediate issue is the newly introduced NULL dereference race.

## 3. Reachability analysis

The read side may be reachable by local users through hwmon sysfs files, depending on permissions. The teardown side is typically privileged or platform/hardware driven. Containers and namespaces usually do not change reachability unless hwmon sysfs is exposed into the container and device removal can be influenced externally.

The issue is not network reachable. Realistic exploitation is timing-dependent local DoS, not privilege escalation.

## 4. Severity interpretation

This behaves like a borderline Moderate availability issue. The strongest supported primitive is a NULL pointer dereference during sysfs teardown. The original UAF concern is disputed and not demonstrated by this revert. There is no supported evidence of arbitrary write, controlled UAF reclaim, information disclosure, or LPE.

## 5. One-sentence report phrase

A reverted ibmpex teardown ordering change could let a concurrent local hwmon sysfs read race with driver data clearing and trigger a NULL pointer dereference, causing kernel DoS.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the patch is a revert of an incomplete UAF-related fix and the exact lifetime risk is disputed, although current evidence mainly supports DoS from a teardown race.

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

Patch: Revert "hwmon: (ibmpex) fix use-after-free in high/low store" [ Upstream
Commit: 05112ba67c824ab416cd54307c0b50aba9f0047a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=05112ba67c824ab416cd54307c0b50aba9f0047a

Changed files:
  drivers/hwmon/ibmpex.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=05112ba67c824ab416cd54307c0b50aba9f0047a

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

The original Linux kernel CVE announcement for CVE-2026-45914 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45914

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: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: 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).