[CVE-2026-93256][LOW] arm64: hibernate: mask DAIF before restoring hibernated kernel [ Upstream

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

CVE: CVE-2026-93256
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: arm64: hibernate: mask DAIF before restoring hibernated kernel [ Upstream
Commit: c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93256
Analysis date: Thu, 24 Sep 2026 19:15:16 -0400
ActionableScore: 0
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-2026-93256 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93256

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-2026-93256	LOW	https://www.kernelcve.org/list/?q=CVE-2026-93256 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:H/UI:N/S:U/C:N/I:N/A:H';CWE-703;CWE-754;BEST CVSS score: '4.1';DESCR 'An arm64 hibernation resume can leave Debug, SError, and pseudo-NMI exceptions unmasked while the old and resumed kernels are temporarily in an inconsistent state. An exception in this window can enter code without a valid executable exception vector mapping and cause a fatal kernel crash. For the CVSS the PR:H is used because initiating hibernation or controlling the relevant system power path normally requires administrative privileges such as CAP_SYS_ADMIN. The issue is local and not network reachable. Exploitation also requires a narrow timing window and an applicable exception event, so AC:H is appropriate. Impact is denial of service only. The patch context does not support confidentiality impact, integrity impact, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	YES	INIT WARNONLY HARDWARE 	NO	NO	checked

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

ActionableScore=0
PrimitiveClass=NONE
RealUAF=NO
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: -2
* Conservative score: 0
* Raw paranoid score: -2
* Paranoid score: 0
* Score range clamp applied: -2 -> 0
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Reliable kernel crash / strong DoS. The patch explicitly states that a Debug, SError, or pseudo-NMI exception during the vulnerable resume window is fatal and silent.
* -2 Host-admin-equivalent requirement. Creating and resuming a hibernation image is a global system power-management operation normally requiring host CAP_SYS_ADMIN or equivalent host administrative authority.
* -1 Hard timing / special event requirement. The failure requires an applicable exception to arrive during a short kernel restore interval while the old and resumed kernels are inconsistent.

Not awarded:

* No UAF, dangling pointer, stale object, refcount misuse, OOB access, invalid free, or memory corruption primitive is established.
* No controlled reclaim, arbitrary write, structured object replacement, callback control, or attacker-controlled post-free state is established.
* No confidentiality or integrity point is awarded. The documented consequence is fatal exception handling during resume, not disclosure or unauthorized modification.
* No remote reachability point is awarded. Packet traffic does not reach this path.
* No local-unprivileged trigger point is awarded. The complete hibernation operation is host power-management control.
* No extra availability point is awarded because the fatal crash is already counted once.

3. Reachability analysis

The triggering path is arm64 suspend-to-disk resume in `swsusp_arch_resume()`. A hibernation image must first be created and later restored through the global hibernation path, which is host-admin-equivalent power-management control.

The affected system must be arm64 with hibernation support in use. The crash additionally requires Debug, SError, or pseudo-NMI exception delivery during the narrow restore interval. Pseudo-NMI increases relevant exception exposure when enabled, but Debug and SError handling are relevant independently.

The operation is not namespace-scoped. A user namespace, network namespace, container, or delegated network capability cannot independently create and restore a host hibernation image. No network trigger, special device input path, firmware compromise, or attacker-controlled exception source is established by the supplied patch.

4. Primitive and severity interpretation

The exact defect is inconsistent DAIF exception masking during arm64 hibernation resume. The restored kernel assumes all DAIF exceptions remain masked, but the pre-fix resume path can permit Debug, SError, or pseudo-NMI exceptions before the resumed kernel reaches a consistent state and before valid executable exception-vector mappings are available.

This is not an active structured-object lifetime issue or fixed stale-storage UAF. It is not a cleanup/destructor bug and contains no concrete repeated release, refcount, free, put, or ownership mutation. The demonstrated consequence is a fatal kernel crash or warning during resume.

PrimitiveClass is NONE because no meaningful corruption, authorization bypass, ownership violation, or lifetime primitive is established. ImportantCandidate is NO because the patch supports a privileged local crash scenario only. AutoDowngradeAllowed is YES because there is no unresolved corruption or security-boundary primitive that would be lost by treating this as an ordinary low-priority availability issue.

5. One-sentence report phrase

An arm64 hibernation resume may take an unmasked Debug, SError, or pseudo-NMI exception while the restored kernel is inconsistent, causing a fatal local kernel crash, but the path requires host-level hibernation control and no memory-corruption or privilege-escalation primitive is established.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes a constrained host-admin-triggered availability failure with a narrow exception timing requirement and no demonstrated corruption, disclosure, integrity impact, or privilege-boundary bypass.

7. Call-site confidence

Call-site confidence: medium

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

Patch: arm64: hibernate: mask DAIF before restoring hibernated kernel [ Upstream
Commit: c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec

Changed files:
  arch/arm64/kernel/hibernate.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=c9c671e9ab87b639720db8f7f8648bdf0f3bc8ec

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

The original Linux kernel CVE announcement for CVE-2026-93256 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-93256

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: Not available
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.1

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: 0

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).