[CVE-2026-97446][LOW] ACPICA: Fix NULL pointer dereference in acpi_ns_custom_package() [ Upstream

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

CVE: CVE-2026-97446
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ACPICA: Fix NULL pointer dereference in acpi_ns_custom_package() [ Upstream
Commit: 3762c6c8ae5073892d7cec736cc54270c7c9ce90
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3762c6c8ae5073892d7cec736cc54270c7c9ce90
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97446
Analysis date: Thu, 24 Sep 2026 18:01:26 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-97446 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97446

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-2026-97446	LOW	https://www.kernelcve.org/list/?q=CVE-2026-97446 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:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.1';DESCR 'A NULL pointer dereference in ACPICA acpi_ns_custom_package can occur when firmware returns a malformed BIX package whose first version element is an unresolvable reference evaluated as NULL. The custom package processing path preserves NULL entries because removing them would shift fixed position fields, and the version element is then dereferenced without validation. This can crash the kernel and cause denial of service. For the CVSS the PR:N is used for the paranoid score because malformed firmware data can be processed automatically during ACPI battery initialization or a firmware event without requiring a local user action. Exploitation requires a system with malformed or attacker controlled ACPI firmware, or a virtual machine environment where platform firmware tables are controlled by the host. No confidentiality or integrity impact is supported because the defect is a NULL pointer dereference without a demonstrated memory corruption primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	DANGER NULLPTR SIMPLEFIX IMPROVEONLY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Firmware-mediated external influence. The NULL element originates from malformed ACPI firmware data rather than an ordinary local syscall input.
* +1 Reliable kernel crash or strong DoS. Dereferencing a NULL package element in ACPICA can cause an Oops or panic.
* +0 No memory corruption primitive. The patch establishes a NULL pointer dereference only.
* +0 Controlled reclaim is not demonstrated.
* +0 Arbitrary write is not demonstrated.
* +0 Confidentiality and integrity impact are not established.
* +0 Remote reachability is not established. Firmware mediation is a material prerequisite.
* +0 Local unprivileged trigger is not established. A local user might cause battery information to be read, but the supplied evidence does not establish that this is sufficient to control the malformed firmware condition.
* +0 No hard race penalty. This is not a race condition.
* +0 No host-admin penalty. Host-admin-equivalent firmware modification is not positively established as a requirement for every affected deployment.

3. Reachability analysis

The vulnerable path processes the ACPI _BIX battery-information package. The immediate malformed input is supplied by platform firmware or by virtual firmware tables presented to a guest.

The supplied patch does not establish that an ordinary local user can create or modify the relevant ACPI package. On physical systems, installing malicious firmware normally requires a separate firmware-control or physical-access capability, but this prerequisite is not sufficiently resolved to mark HostAdminRequired as YES.

In virtualized environments, a hypervisor or VM host can provide ACPI firmware data to a guest. This is firmware-mediated influence, not direct network reachability and not a demonstrated guest-to-host vulnerability. No namespace-scoped privilege path is involved.

4. Primitive and severity interpretation

The exact primitive is a NULL pointer dereference in acpi_ns_custom_package when the first _BIX package element evaluates to NULL and is subsequently dereferenced as an ACPI operand object.

This is neither a UAF nor an ownership or refcount lifetime violation. There is no stale object, object reuse, post-free access, controlled replacement, out-of-bounds access, arbitrary write, callback influence, information disclosure, or authorization bypass.

The demonstrated consequence is kernel crash or denial of service on a system with malformed or attacker-controlled ACPI firmware data. A stronger consequence such as privilege escalation or kernel memory corruption is speculative and unsupported by the patch.

PrimitiveClass is CLASS_C because the established behavior is invalid-state handling followed by a crash. ImportantCandidate is NO because no meaningful exploitation leverage beyond DoS is demonstrated. AutoDowngradeAllowed is YES because the issue is a constrained crash-only NULL dereference without unresolved corruption or security-boundary primitive.

5. One-sentence report phrase

A malformed firmware supplied BIX package can cause a NULL pointer dereference in ACPICA and crash the kernel, resulting in denial of service without a demonstrated memory corruption or privilege escalation primitive.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes a firmware-mediated NULL pointer dereference with DoS impact only. No UAF, overwrite, disclosure, authorization bypass, or meaningful unresolved exploitation primitive is shown.

7. Call-site confidence

Call-site confidence: medium

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

Patch: ACPICA: Fix NULL pointer dereference in acpi_ns_custom_package() [ Upstream
Commit: 3762c6c8ae5073892d7cec736cc54270c7c9ce90
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3762c6c8ae5073892d7cec736cc54270c7c9ce90

Changed files:
  drivers/acpi/acpica/nsprepkg.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=3762c6c8ae5073892d7cec736cc54270c7c9ce90

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

The original Linux kernel CVE announcement for CVE-2026-97446 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97446

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:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.1

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: 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).