* [CVE-2026-100072][MODERATE REGULAR] ACPI: platform: Use acpi_bus_get_primary_device() [ Upstream
@ 2026-09-25 14:14 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-25 14:14 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-100072
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ACPI: platform: Use acpi_bus_get_primary_device() [ Upstream
Commit: c9d202d3b6c28e8c779cd2f2b10d2f7ab665ca71
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9d202d3b6c28e8c779cd2f2b10d2f7ab665ca71
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-100072
Analysis date: Fri, 25 Sep 2026 10:14:18 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
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-2026-100072 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-100072
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-2026-100072 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-100072 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:H/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'An ACPI platform device creation path can use a physical struct device pointer returned without a retained device reference. The referenced device can theoretically be released concurrently, leaving code in resource handling or platform device creation with a stale pointer and creating a potential use after free condition. The most likely result is a kernel crash or denial of service during ACPI device lifecycle activity. For the CVSS the PR:H is used because reliably reaching this path normally requires administrative control over ACPI device lifecycle operations, driver binding, hotplug like events, or privileged system configuration. The issue is not directly network reachable. Impact is at least a local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to the use after free condition and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 4) YES OOB INIT UAF HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
1. ActionableScore
* Raw conservative score: 2
* Conservative score: 4
* Raw paranoid score: 2
* Paranoid score: 4
* Applied conservative floor: Real UAF floor 4 changed the score from 2 to 4.
* Applied paranoid floor: Real UAF floor 4 changed the score from 2 to 4.
* Final recommended bucket: **Borderline / manual review recommended**::
2. Signal breakdown
* +2 Real UAF or lifetime violation. `acpi_get_first_physical_node()` returns a `struct device` pointer without retaining a device reference. The patch explicitly states that the returned device may be freed at any time, while the old code subsequently uses the pointer in `dev_is_pci()`, `pci_find_resource()`, and as `pdevinfo.parent`.
* +0 Reliable kernel crash or strong DoS not awarded. The patch identifies an unsafe lifetime condition but does not provide an observed Oops, KASAN report, panic, or proven crash path.
* +0 Local unprivileged trigger not awarded. The supplied code and commit do not establish that an ordinary local user can trigger the complete ACPI physical-device removal and platform-device-creation sequence.
* +0 Remote reachability not awarded. This is not a network-facing path.
* +0 Structured stale-object exploitation leverage not awarded. `struct device` is an active structured kernel object, but the patch does not establish attacker-controlled replacement, post-free contents, callback dispatch, meaningful stale-field consumption after reuse, or a controlled type-confusion mechanism.
* +0 Strong exploitation leverage not awarded. Controlled reclaim, arbitrary or directed kernel write, refcount takeover, disclosure, and privilege escalation are not demonstrated.
* +0 Concrete repeated release/refcount mutation not awarded. The patch adds one retained reference through `acpi_bus_get_primary_device()` and releases it once through `put_device()` at function exit. It does not establish an earlier release followed by a second lifetime-mutating operation on the same dangling reference.
* +0 Confidentiality and integrity impact not awarded. A theoretical stale `struct device` dereference does not itself establish an information disclosure, unauthorized modification, or protected-resource access primitive.
* No negative race penalty was applied. The commit describes an object-lifetime race, but does not establish a narrow, externally uncontrollable, one-shot timing condition.
* No host-admin penalty was applied. Administrative privilege may be relevant in practical ACPI device lifecycle scenarios, but the complete privilege boundary is not established by the supplied evidence.
3. Reachability analysis
The vulnerable path is entered while creating an ACPI platform device and obtaining its parent physical device. The unsafe operation requires a concurrent lifetime transition in which the physical parent device is removed or freed after `acpi_get_first_physical_node()` returns its unreferenced pointer and before all later pointer uses complete.
The supplied patch does not show who can induce ACPI device removal, driver unbinding, hotplug processing, platform-device creation, or the required concurrent sequencing. Therefore, host-admin-equivalent privilege cannot be positively established, but below-host-admin reachability also cannot be established.
No namespace-specific capability checks, network namespace operations, container path, or attacker-creatable namespace-local object path are shown. NamespaceScopedPrivilege is therefore UNKNOWN.
There is no demonstrated prior firmware compromise, special hardware requirement, direct external-device input, or network trigger. ACPI is broadly deployed, but this specific lifetime race depends on device-management activity and cannot be treated as broadly attacker-reachable based on the patch alone.
4. Primitive and severity interpretation
The exact primitive is a potential stale `struct device` use caused by failure to retain a device reference. The old code obtains a raw physical-device pointer, then uses it for PCI resource lookup and as the parent of a newly created platform device. Concurrent device release can invalidate that pointer.
This is an active structured-object lifetime issue rather than fixed stale storage. However, the visible stale uses are shallow resource and parent-device operations. The patch does not establish attacker-controlled reuse of the freed allocation, attacker-shaped replacement contents, stale callback invocation, arbitrary read or write, or a second lifetime/refcount mutation through the same dangling reference.
This is therefore CLASS_B, not CLASS_A. The demonstrated primitive is stronger than an ordinary invalid-value bug because a kernel object can lose lifetime protection while remaining in use. Nevertheless, the available evidence supports only an unresolved potential stale dereference, with kernel crash or DoS as the plausible operational consequence.
ImportantCandidate is NO because meaningful exploitation leverage beyond a stale-object fault is not established. Manual review remains recommended because the fix is explicitly a reference-lifetime correction around a kernel `struct device` pointer. AutoDowngradeAllowed is YES because this is not a concrete repeated-release case, does not establish controlled reclaim or a write primitive, and does not demonstrate a boundary bypass.
5. One-sentence report phrase
An ACPI platform device creation path could use a physical device pointer without holding a device reference, allowing a concurrent device release to cause a potential stale pointer dereference and local kernel denial of service.
6. Manual review recommendation
MANUAL CHECK RECOMMENDED
The patch establishes a real kernel object lifetime violation, but supplied evidence does not establish attacker reachability, a reliable crash, controlled post-free reuse, a write primitive, or privilege escalation.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ACPI: platform: Use acpi_bus_get_primary_device() [ Upstream
Commit: c9d202d3b6c28e8c779cd2f2b10d2f7ab665ca71
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9d202d3b6c28e8c779cd2f2b10d2f7ab665ca71
Changed files:
drivers/acpi/acpi_platform.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=c9d202d3b6c28e8c779cd2f2b10d2f7ab665ca71
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-100072 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-100072
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:H/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 6.4
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: 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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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