[CVE-2026-45968][LOW] cpuidle: Skip governor when only one idle state is available [ Upstream

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

CVE: CVE-2026-45968
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: cpuidle: Skip governor when only one idle state is available [ Upstream
Commit: a0f7e804edc82e513d1ccb7c95ed8b351522ec81
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a0f7e804edc82e513d1ccb7c95ed8b351522ec81
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45968
Analysis date: Wed, 27 May 2026 09:33:38 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-45968 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45968

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: LOW
Manual review required: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-45968	LOW	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-476;CWE-129;CWE-754;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'cpuidle can crash on specific PowerNV configurations when only one idle state is registered and the governor still selects a non existing state 1. This can lead to an out of bounds idle state selection and a NULL enter callback invocation at address 0. For the CVSS the PR:L is used for the paranoid case because a local workload may help trigger idle transitions on an already affected system, although the root cause is platform configuration rather than user controlled input. The issue is not network reachable and has no evidence of memory corruption, information disclosure, or privilege escalation. Impact is denial of service only through a platform specific kernel crash.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	WRITE OOB DANGER SIMPLEFIX KERNEL_PANIC_PLUS_UAF HARDWARE  LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2
ActionableScoreLower=0

1. ActionableScore
* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

2. Signal breakdown
* Reliable kernel crash / strong DoS: +1. The bug can invoke a NULL enter callback and crash the kernel on affected systems.
* Availability impact realistic: +1 in paranoid scoring. The crash is real on the specific PowerNV configuration described.
* Local workload influence: +1 in paranoid scoring. A local workload may help the system enter idle paths, but it does not control the root cause.
* Physical or rare hardware/platform-specific condition: -2. The issue is tied to certain PowerNV systems without a power-mgt DT node and only one registered cpuidle state.
* No memory corruption: +0. This is an out-of-bounds state selection leading to a NULL callback, not UAF, OOB write, arbitrary write, or controlled corruption.
* No privilege escalation: +0. No LPE primitive is shown.
* No network reachability: +0. The path is not remotely triggerable.

3. Reachability analysis
The bug is primarily triggered by platform configuration: PowerNV systems where cpuidle registers only a single idle state, especially when that state is polling state 0. It may manifest automatically during boot or normal idle transitions. A local user may indirectly encourage idle transitions by changing workload patterns, but cannot create the vulnerable configuration in normal deployments. Containers and namespaces do not meaningfully affect reachability. The issue is not network reachable.

4. Severity interpretation
This behaves like a Low-like or ordinary Moderate platform-specific DoS. The realistic impact is a kernel crash on affected hardware/configuration. There is no evidence of memory corruption, information disclosure, privilege escalation, or attacker-controlled exploitation beyond inducing idle behavior on an already vulnerable platform.

5. One-sentence report phrase
On specific PowerNV configurations with only one cpuidle state, the governor may select a non-existent idle state and invoke a NULL enter callback, causing a platform-specific kernel crash.

6. Manual review recommendation
NO MANUAL CHECK NEEDED
The issue is DoS-only, hardware/configuration-specific, and has no demonstrated memory corruption, remote trigger, or privilege escalation primitive.

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

Patch: cpuidle: Skip governor when only one idle state is available [ Upstream
Commit: a0f7e804edc82e513d1ccb7c95ed8b351522ec81
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a0f7e804edc82e513d1ccb7c95ed8b351522ec81

Changed files:
  drivers/cpuidle/cpuidle.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=a0f7e804edc82e513d1ccb7c95ed8b351522ec81

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

The original Linux kernel CVE announcement for CVE-2026-45968 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45968

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: 0
  Paranoid ActionableScore: 2

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

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).