[CVE-2026-90228][MODERATE REGULAR] nvmet: fix NULL pointer dereference in nvmet_execute_identify_ns_zns() [ Upstream

[CVE-2026-90228][MODERATE REGULAR] nvmet: fix NULL pointer dereference in nvmet_execute_identify_ns_zns() [ Upstream

[AL-KERNEL]

CVE: CVE-2026-90228
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: nvmet: fix NULL pointer dereference in nvmet_execute_identify_ns_zns() [ Upstream
Commit: 1ce8faf90eb0bf5599b90db38500aefea9426485
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1ce8faf90eb0bf5599b90db38500aefea9426485
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90228
Analysis date: Thu, 17 Sep 2026 20:18:26 -0400
ActionableScore: 3
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-2026-90228 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90228

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-2026-90228	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-90228 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-476;*CWE-20;CWE-754;BEST CVSS score: '6.5';DESCR 'A NULL pointer dereference in the NVMe target ZNS Identify path occurs because nvmet_execute_identify_ns_zns() can call bdev_is_zoned() with req ns bdev set to NULL for a file backed namespace. A remote or fabric attached NVMe host can trigger this by sending an Identify command with CNS 05h and CSI 02h for ZNS against a file backed namespace when CONFIG_BLK_DEV_ZONED is enabled. For the CVSS the PR:N because no local user privileges on the target are required beyond access to the exposed NVMe target interface. The attack is not a local syscall path on the target and is reachable from an authorized or network adjacent NVMe host in a storage fabric. Impact is denial of service via target kernel crash. No UAF, OOB write, arbitrary write, or information leak primitive is visible from the patch context, so confidentiality and integrity remain N even for the paranoid score.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)	YES	NULLPTR SIMPLEFIX NVME HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4	NO	NO	checked

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

ActionableScore=3
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 3
* Conservative score: 3. No floor or cap applied.
* Raw paranoid score: 3
* Paranoid score: 3. No floor or cap applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Positive signals:

* +2 Remote or fabric reachable trigger: an NVMe host with access to the NVMe target can send an Identify command with CNS 05h and CSI 02h to reach the vulnerable ZNS Identify path.
* +1 Reliable kernel crash / strong DoS: bdev_is_zoned() is called with req->ns->bdev equal to NULL for file-backed namespaces, causing a NULL pointer dereference and target kernel oops/crash.

Negative signals:

* No negative privilege penalty: host-admin-equivalent privilege on the target is not required for the attacking NVMe host once the target interface is reachable.
* No race penalty: this is an ordered invalid-input/state-validation bug, not a timing race.
* No rare-hardware penalty: NVMe target/ZNS is specialized, but no unusual physical-only hardware prerequisite is established.

Important non-awarded signals:

* RealUAF not awarded: no use-after-free or stale post-lifetime object use is shown.
* Controlled reclaim not demonstrated.
* Arbitrary or directed kernel write not demonstrated.
* Confidentiality and integrity signals not awarded: no information leak, object overwrite, ownership violation, or privilege escalation primitive is visible.
* Extra availability not awarded: the same kernel crash is already counted once.
* ImportantCandidate not set: this is a direct NULL pointer dereference with DoS impact, not unresolved memory corruption.
* AutoDowngradeAllowed remains YES because the primitive is CLASS_C crash-only behavior without unresolved corruption leverage.

3. Reachability analysis

The attacker is a remote or fabric-attached NVMe host that can issue commands to the configured NVMe target. The vulnerable command is host-supplied and reaches nvmet_execute_identify_ns_zns() when CONFIG_BLK_DEV_ZONED is enabled and the namespace is file-backed. The attacker does not need local code execution or administrative privilege on the target host, so HostAdminRequired=NO.

Namespace-scoped privilege is not relevant here. This is not a local namespace capability path, and no user namespace or network namespace requirement is involved.

There is prior administrative setup in the normal sense that an NVMe target and a file-backed namespace must already exist and be exposed to the host. That is a deployment condition for the service, not evidence that the attacker needs target host-admin privilege. NVMe/TCP or NVMe fabric targets are commonly restricted to storage or data-center networks, so practical exposure depends on whether untrusted hosts can reach the target listener.

No race is required. The trigger is a malformed or semantically invalid Identify Namespace ZNS request against an incompatible backing type.

4. Primitive and severity interpretation

The exact primitive is a NULL pointer dereference of req->ns->bdev through bdev_is_zoned(). The namespace is file-backed, so req->ns->bdev is NULL. The ZNS Identify handler did not reject that state before calling the block-device helper.

This is not active structured UAF and not fixed stale storage. It is a direct invalid dereference caused by missing state validation.

PrimitiveClass=CLASS_C because the demonstrated behavior is crash/DoS only. The demonstrated consequence is target kernel oops/crash. The speculative consequence would be broader impact only if additional memory corruption were found, but the patch context does not support UAF, OOB access, arbitrary write, controlled replacement, or information disclosure.

ImportantCandidate=NO because there is no unresolved kernel corruption primitive beyond the NULL dereference. AutoDowngradeAllowed=YES because automatic downgrade to ordinary or borderline Moderate does not discard a meaningful unresolved exploitation primitive. Operationally, this is still worth review when NVMe target services are reachable by untrusted or semi-trusted storage hosts.

5. One-sentence report phrase

A fabric-attached NVMe host can crash an NVMe target by sending a ZNS Identify Namespace command to a file-backed namespace, causing bdev_is_zoned() to dereference a NULL backing block device.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: the bug is crash-only and has no demonstrated memory corruption primitive, but it is reachable through an NVMe target fabric interface and can remotely crash the target kernel in exposed storage deployments.

7. Call-site confidence

Call-site confidence: high

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

Patch: nvmet: fix NULL pointer dereference in nvmet_execute_identify_ns_zns() [ Upstream
Commit: 1ce8faf90eb0bf5599b90db38500aefea9426485
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1ce8faf90eb0bf5599b90db38500aefea9426485

Changed files:
  drivers/nvme/target/zns.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=1ce8faf90eb0bf5599b90db38500aefea9426485

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

The original Linux kernel CVE announcement for CVE-2026-90228 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90228

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:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 6.5

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: unknown
  Paranoid ActionableScore: 3

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).