[CVE-2026-93093][LOW] firmware: arm_scmi: Publish channel state before callbacks [ Upstream

[CVE-2026-93093][LOW] firmware: arm_scmi: Publish channel state before callbacks [ Upstream

[AL-KERNEL]

CVE: CVE-2026-93093
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: firmware: arm_scmi: Publish channel state before callbacks [ Upstream
Commit: 6f3f532531e4a27d28a2240719d1b05ac11766c6
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6f3f532531e4a27d28a2240719d1b05ac11766c6
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93093
Analysis date: Thu, 17 Sep 2026 21:55:12 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-93093 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93093

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-2026-93093	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93093 CHECK WITH IMPACT FROM ORIG NN LOW	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-362;**CWE-476;CWE-665;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A race in ARM SCMI channel setup can allow mailbox or SMC transport callbacks to run before the channel state is fully published. The RX path may then dereference a NULL transport cinfo pointer or a NULL cinfo handle, causing a kernel crash. For the CVSS the PR:L is used in the paranoid score because a delegated service account or reduced admin context may be able to trigger driver reprobe or transport setup paths in some embedded or platform management environments. The issue is not network reachable and is tied to local platform setup, mailbox callbacks, or SMC completion IRQ delivery. Impact is denial of service only because the evidence points to NULL pointer dereference and initialization ordering, not UAF, OOB access, information disclosure, or an arbitrary write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	INIT HARDWARE LINUS 	YES	NO	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate**::

No floor or cap changed the score.

2. Signal breakdown

Conservative signals:

* +1 Reliable kernel crash / strong DoS: an early mailbox or SMC callback can dereference a NULL transport cinfo pointer or NULL cinfo handle in the SCMI RX path.
* +0 Weak corruption concern: this is a NULL pointer dereference and initialization ordering bug, not a demonstrated UAF, OOB access, arbitrary write, or controlled object corruption.

Paranoid additional signal:

* +1 Firmware-mediated external influence: the callback source is tied to mailbox controller startup or optional SMC A2P IRQ delivery, so platform or firmware mediated interrupt behavior is material to the trigger.

Non-awarded signals:

* UAF not awarded: no object is shown as freed and later reused.
* Concrete repeated release/refcount not awarded: no first put/free followed by a second lifetime mutation on the same dangling reference is shown.
* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Confidentiality and integrity impact not awarded because the established primitive is NULL dereference only.
* Remote reachability not established.
* Extra availability point not awarded because the same crash is already counted once.
* Race penalty not applied because the issue is already limited by unclear attacker reachability and no attacker-controlled hard timing sequence is established.

3. Reachability analysis

The trigger occurs during ARM SCMI channel setup. The relevant window is after transport setup has enabled callbacks or IRQ delivery but before SCMI channel state is fully published.

A normal remote network attacker cannot reach this path. The issue is local platform or firmware mediated, involving mailbox callbacks or SMC completion IRQ delivery.

The complete attacker model is unresolved. A host administrator could likely exercise setup paths through driver bind, reprobe, reboot, or platform management actions, but the supplied evidence does not prove that host-admin-equivalent privilege is strictly required for every possible occurrence. Below-host-admin reachability is also not established.

NamespaceScopedPrivilege is NO because SCMI firmware transport setup is not a namespace-scoped network or user namespace operation.

Prior platform configuration and ARM SCMI-capable hardware or firmware are prerequisites. This is hardware and platform dependent, but the evidence does not justify a separate rare-hardware penalty.

Race repeatability is uncertain. The bug depends on an early pending or spurious callback in a setup window, but no attacker-controlled repeated race loop is established.

4. Primitive and severity interpretation

The exact primitive is a NULL pointer dereference caused by publishing SCMI channel state too late relative to callback or IRQ enablement.

This is not active structured UAF. It is not fixed stale storage either. It is an initialization ordering race where an otherwise valid callback path observes partially initialized channel state.

There is no concrete repeated release/refcount operation. No first lifetime operation is shown to destroy an object, and no second operation mutates a potentially freed object.

PrimitiveClass is CLASS_C because the demonstrated behavior is invalid state leading to NULL dereference and kernel crash.

Demonstrated consequence: local or platform-mediated denial of service via kernel crash.

Speculative consequence: stronger exploitation is not supported by the patch because there is no stale object reuse, no controlled memory corruption, no disclosure path, and no authorization bypass.

ImportantCandidate is NO because the established primitive is crash-only and does not leave meaningful unresolved exploitation leverage beyond NULL dereference.

AutoDowngradeAllowed is YES because this is a constrained CLASS_C DoS issue with no UAF, no repeated lifetime mutation, no controlled corruption, and no security-boundary bypass.

Likely operational severity is ordinary Moderate or Low-like depending on whether the affected platform can actually hit the early callback window.

5. One-sentence report phrase

ARM SCMI channel setup can enable mailbox or SMC callbacks before the channel state is fully published, allowing an early callback to dereference a NULL cinfo or handle pointer and crash the kernel.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch-supported primitive is NULL dereference during setup, with no UAF, no arbitrary read or write, no privilege escalation path, and no direct remote reachability.

7. Call-site confidence

Call-site confidence: medium

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

Patch: firmware: arm_scmi: Publish channel state before callbacks [ Upstream
Commit: 6f3f532531e4a27d28a2240719d1b05ac11766c6
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6f3f532531e4a27d28a2240719d1b05ac11766c6

Changed files:
  drivers/firmware/arm_scmi/driver.c
  drivers/firmware/arm_scmi/transports/mailbox.c
  drivers/firmware/arm_scmi/transports/smc.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=6f3f532531e4a27d28a2240719d1b05ac11766c6

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

The original Linux kernel CVE announcement for CVE-2026-93093 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93093

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).