[CVE-2026-72432][LOW] tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream

[CVE-2026-72432][LOW] tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream

[AL-KERNEL]

CVE: CVE-2026-72432
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream
Commit: c041d2be785feb9b5e36331921eadaefbe65349d
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c041d2be785feb9b5e36331921eadaefbe65349d
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72432
Analysis date: Sun, 16 Aug 2026 07:02:00 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
`tpm_crb can dereference a missing ACPI companion when forced to bind to an unsuitable platform device via driver_override, allowing a local administrator or delegated device-management actor to trigger a kernel crash, with no evidence of confidentiality impact, integrity impact, or privilege escalation.`

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

The original Linux kernel CVE announcement for CVE-2026-72432 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72432

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-2026-72432	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	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-476;*CWE-20;CWE-703;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'tpm_crb assumed that a probed platform device always has an ACPI companion object. A local actor who can force driver binding through driver_override can make the platform driver match a device that is not backed by the expected ACPI data, which may lead to a NULL pointer dereference during probe and cause a kernel oops or crash. For the CVSS the PR:L is used in the paranoid score because some environments may delegate limited device management or sysfs binding control to a service account or reduced capability administrator, although PR:H is more typical on standard systems. The issue is not network reachable and requires local control over driver binding rather than packet input. Impact is denial of service only via kernel crash or oops, with no supported confidentiality or integrity impact from the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)  SKIP CVE-2026-72432 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: 48fe2cddc85c7849463bd01ae8b8c6b575ff508b YES  NO NO unknown 	MAYBE	SIMPLEFIX HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. Forced probing of `tpm_crb` against a non matching platform device without an ACPI companion can plausibly cause a NULL pointer dereference during probe.
* Requires admin/root/CAP_* in typical deployments: -2. The practical trigger is `driver_override` or manual driver bind through sysfs, which is normally root/admin controlled.
* Rare and difficult-to-reach path: -1. This is not normal TPM operation. It requires forced driver matching against an unsuitable device.

Conservative raw result is negative, treated as 0 for practical bucket interpretation.

Paranoid signals:

* Reliable kernel crash / strong DoS: +1. A delegated device-management service account or reduced-capability admin could potentially trigger the bad bind in some environments.
* No memory corruption bonus. The patch only supports a NULL companion validation failure and NULL dereference style crash, not UAF, OOB write, double free, type confusion, refcount abuse, or controlled overwrite.
* No confidentiality or integrity impact. There is no supported leak, write primitive, credential access, TPM secret exposure, or privilege escalation path.
* No network or firmware-mediated external influence. The affected path is local driver binding, not packet input or firmware-fed parsing.

## 3. Reachability analysis

The bug is triggerable by a local actor able to force platform driver matching through `driver_override` or equivalent sysfs bind operations. In ordinary deployments this requires administrator privileges on the host. Namespaces or containers normally should not expose host driver binding controls, but a reduced-privilege device-management service or unusually delegated sysfs access could make the paranoid PR:L interpretation reasonable. The TPM CRB driver may be present on many systems, but the vulnerable condition is not default operation and depends on intentionally binding the driver to a device without the expected ACPI companion.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like local DoS issue, not an Important-class vulnerability. The realistic impact is a kernel oops or crash during probe. Theoretical severity does not extend beyond DoS based on the patch because the fix is a straightforward NULL check and there is no evidence of attacker-controlled memory reuse, stale pointer lifetime corruption, arbitrary write, information disclosure, or privilege escalation.

## 5. One-sentence report phrase

`tpm_crb can dereference a missing ACPI companion when forced to bind to an unsuitable platform device via driver_override, allowing a local administrator or delegated device-management actor to trigger a kernel crash, with no evidence of confidentiality impact, integrity impact, or privilege escalation.`

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a local forced-driver-bind NULL dereference with admin-level reachability in normal deployments and no supported memory corruption or security-boundary bypass primitive.

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

Patch: tpm_crb: Check ACPI_COMPANION() against NULL during probe [ Upstream
Commit: c041d2be785feb9b5e36331921eadaefbe65349d
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c041d2be785feb9b5e36331921eadaefbe65349d

Changed files:
  drivers/char/tpm/tpm_crb.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=c041d2be785feb9b5e36331921eadaefbe65349d

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

The original Linux kernel CVE announcement for CVE-2026-72432 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72432

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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  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: 0
  Paranoid ActionableScore: 1

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).