[CVE-2026-64511][LOW] ACPI: NFIT: core: Fix possible NULL pointer dereference

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

CVE: CVE-2026-64511
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ACPI: NFIT: core: Fix possible NULL pointer dereference
Commit: a44343fe230aa48c74ef09830f3c5c90848b257e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a44343fe230aa48c74ef09830f3c5c90848b257e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64511
Analysis date: Sat, 25 Jul 2026 08:18:48 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
ACPI NFIT may dereference a NULL descriptor when firmware sends a UC memory error notification after handler installation but before NFIT driver data exists, causing a firmware-mediated local DoS via kernel crash.

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

The original Linux kernel CVE announcement for CVE-2026-64511 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64511

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-2026-64511	LOW	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:N/I:N/A:H';**CWE-476;CWE-665;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 'ACPI NFIT can dereference a NULL descriptor in acpi_nfit_uc_error_notify when the Notify handler is installed but the NFIT table is absent and no driver data was created for the device. A firmware generated UC memory error notification can then enter the handler and access acpi_desc scrub_mode while acpi_desc is NULL, causing a kernel crash or oops. For the CVSS the PR:L is used for the paranoid score because a local service or reduced capability admin context may be able to provoke ACPI notification paths on some platforms, while the normal reliable trigger is firmware or administrator controlled. The issue is not network reachable and does not provide an evident information disclosure or privilege escalation primitive. Impact is denial of service only.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2)	YES	NULLPTR SIMPLEFIX HARDWARE  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Firmware-mediated external influence: +1. The trigger is an ACPI NFIT notification generated by platform firmware.
* Reliable kernel crash / strong DoS: +1. The handler can dereference NULL acpi_desc and crash or oops the kernel.
* Rare AND difficult-to-reach subsystem/configuration: -1. This requires ACPI NFIT/NVDIMM related platform state, missing NFIT table, and a firmware notification in the vulnerable window.

Paranoid adjustment:

* Availability impact realistic: +1. If the firmware notification is reproducible on an affected platform, the result can be a host kernel crash.
* No memory corruption bonus. This is a NULL pointer dereference, not UAF, OOB write, double free, refcount abuse, or type confusion.
* No LPE bonus. There is no attacker-controlled reclaim, stale object reuse, callback control, arbitrary write, or credential/security-boundary primitive.
* No remote/network bonus. The affected path is ACPI firmware notification handling, not a network reachable parser or packet path.

## 3. Reachability analysis

The most realistic trigger is platform firmware sending NFIT_NOTIFY_UC_MEMORY_ERROR after the notify handler has been installed but before acpi_desc was allocated and stored as device driver data. A normal remote attacker cannot reach this path. A local user generally cannot trigger it without privileged ACPI/platform-management capabilities or special test/debug interfaces. Namespace or container delegation does not normally make ACPI NFIT notifications available to unprivileged users. The affected subsystem is hardware and firmware dependent and is not a broad default user-accessible kernel interface.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like kernel DoS issue. The theoretical impact is a kernel crash from a NULL pointer dereference. There is no realistic evidence of memory corruption beyond invalid NULL dereference, no confidentiality impact, no integrity impact, and no plausible privilege escalation path from the patch context. The issue should not be treated as Important unless external evidence shows an unprivileged way to generate the ACPI notification or a downstream primitive beyond NULL dereference.

## 5. One-sentence report phrase

ACPI NFIT may dereference a NULL descriptor when firmware sends a UC memory error notification after handler installation but before NFIT driver data exists, causing a firmware-mediated local DoS via kernel crash.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a firmware-mediated NULL pointer dereference with DoS-only impact, rare platform dependence, no network reachability, and no supported memory-corruption or privilege-escalation primitive.

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

Patch: ACPI: NFIT: core: Fix possible NULL pointer dereference
Commit: a44343fe230aa48c74ef09830f3c5c90848b257e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a44343fe230aa48c74ef09830f3c5c90848b257e

Commit description:

After commit 9b311b7 ("ACPI: NFIT: Install Notify() handler before
getting NFIT table"), acpi_nfit_probe() installs an ACPI notify handler
for the NFIT device before checking the presence of the NFIT table.  If
that table is not there, 0 is returned without allocating the acpi_desc
object and setting the driver data pointer of the NFIT device.  If the
platform firmware triggers an NFIT_NOTIFY_UC_MEMORY_ERROR notification
on the NFIT device at that point, acpi_nfit_uc_error_notify() will
dereference a NULL pointer.

Prevent that from occurring by adding an acpi_desc check against NULL
to acpi_nfit_uc_error_notify().

Fixes: 9b311b7 ("ACPI: NFIT: Install Notify() handler before getting NFIT table")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: All applicable <stable@vger.kernel.org>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/2418508.ElGaqSPkdT@rafael.j.wysocki
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/acpi/nfit/core.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=a44343fe230aa48c74ef09830f3c5c90848b257e

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

The original Linux kernel CVE announcement for CVE-2026-64511 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64511

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: 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).