[CVE-2026-45855][MODERATE REGULAR] ata: libata-scsi: avoid Non-NCQ command starvation [ Upstream

[CVE-2026-45855][MODERATE REGULAR] ata: libata-scsi: avoid Non-NCQ command starvation [ Upstream

[AL-KERNEL]

CVE: CVE-2026-45855
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ata: libata-scsi: avoid Non-NCQ command starvation [ Upstream
Commit: ce22aaed011206fed9cbd8c9c2d44718607f31ee
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce22aaed011206fed9cbd8c9c2d44718607f31ee
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45855
Analysis date: Wed, 27 May 2026 09:12:30 -0400
ActionableScore: 4
ActionableScore lower bound: 3
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-2026-45855 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45855

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-2026-45855	MODERATE	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';**CWE-400;CWE-667;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'libata-scsi could repeatedly defer non-NCQ commands while sustained NCQ traffic is active on a multi-queue ATA host, causing long delays or complete starvation of commands that cannot be mixed with NCQ. A local user may be able to contribute to the trigger by generating heavy disk I/O and sync or flush style workloads, but reliable reproduction depends on the ATA device, host queueing behavior, and sustained NCQ pressure. For the CVSS the PR:L is used for the paranoid case because ordinary local workloads can influence the storage I/O pattern without full administrator privileges. The issue is not network reachable and does not provide memory corruption, information disclosure, or privilege escalation. Impact is denial of service through storage command starvation and degraded system or application availability.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 4)	YES	LOCK INIT WARNONLY HARDWARE  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

1. ActionableScore
* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended**::

2. Signal breakdown
* Local unprivileged trigger: +1. Ordinary local workloads can create sustained disk I/O and NCQ pressure, although reliable triggering depends on device and queue behavior.
* Reliable strong DoS: +1. The bug can cause very long delays or complete starvation of non-NCQ commands.
* Important filesystem/storage path: +1. The issue affects libata/SCSI command dispatch and storage forward progress.
* Availability impact realistic: +1 in paranoid scoring. Starvation of flush, sync, management, or other non-NCQ commands can degrade applications or storage availability.
* Broad/default/common subsystem: +1 in paranoid scoring. libata is broadly deployed, but the problematic case needs multi-queue host behavior and sustained NCQ traffic.
* Hard or configuration-dependent trigger: -1. Reproduction requires constant NCQ load, non-NCQ commands, and a host/device setup where requeueing can repeatedly lose ordering.
* No memory corruption: +0. The patch fixes starvation and forward progress, not UAF, OOB write, arbitrary write, or object lifetime corruption.
* No privilege escalation: +0. No LPE primitive is shown.

3. Reachability analysis
A local user may influence the bug by generating heavy storage I/O while workloads or system operations issue non-NCQ commands such as flush or sync style commands. No administrator privilege is necessarily required to create I/O pressure, but reliable reproduction depends on the ATA device, libata host configuration, multi-queue behavior, and sustained NCQ traffic. Containers may contribute I/O pressure if they can write to affected storage, but they do not gain a special control primitive. The issue is not network reachable.

4. Severity interpretation
This behaves like a borderline Moderate storage availability issue. It is more actionable than a cosmetic scheduling bug because it can break forward progress for storage commands and cause practical service degradation. It is not Important-class by itself because there is no memory corruption, no information disclosure, no privilege escalation, and no direct remote trigger. The realistic impact is denial of service through storage command starvation.

5. One-sentence report phrase
libata-scsi could indefinitely starve non-NCQ commands under sustained NCQ load on multi-queue ATA hosts, allowing local I/O pressure to cause storage availability degradation without memory corruption or privilege escalation.

6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The issue is DoS-only, but it affects an important storage command path and may be locally triggerable by ordinary I/O workloads on affected multi-queue ATA systems.

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

Patch: ata: libata-scsi: avoid Non-NCQ command starvation [ Upstream
Commit: ce22aaed011206fed9cbd8c9c2d44718607f31ee
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ce22aaed011206fed9cbd8c9c2d44718607f31ee

Changed files:
  drivers/ata/libata-core.c
  drivers/ata/libata-eh.c
  drivers/ata/libata-scsi.c
  drivers/ata/libata.h
  include/linux/libata.h

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=ce22aaed011206fed9cbd8c9c2d44718607f31ee

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

The original Linux kernel CVE announcement for CVE-2026-45855 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45855

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:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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).