[CVE-2026-90206][IMPORTANT] nvmet: fix max_qid race between configfs and controller allocation [ Upstream

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

CVE: CVE-2026-90206
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: nvmet: fix max_qid race between configfs and controller allocation [ Upstream
Commit: 2c23fc91789dfd9db746edb3ae9b90d65fabd410
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2c23fc91789dfd9db746edb3ae9b90d65fabd410
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90206
Analysis date: Thu, 17 Sep 2026 18:29:23 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-90206 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90206

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: IMPORTANT
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-2026-90206	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-90206 CHECK WITH IMPACT FROM ORIG NN IMPORTANT	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-787;CWE-122;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'NVMe target controller allocation can race with configfs qid_max updates. The controller may allocate sqs and cqs arrays using the old smaller max_qid, while later queue validation observes the new larger subsystem max_qid and accepts queue IDs beyond the allocated arrays. This can cause out-of-bounds access in the target queue handling path and may corrupt kernel memory. For the CVSS the PR:L is used for the paranoid score because reduced-capability root, container root, or delegated storage management may be able to modify nvmet configfs without full host administrative control. The issue is mainly local control plane reachable through configfs, while a remote NVMe initiator alone normally cannot change max_qid. Impact is at least denial of service via KASAN warning or kernel crash and in worst case may allow confidentiality or integrity impact due to memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	YES	WRITE KASAN OOB LOCK INIT NVME RACE TIMER DEBUGFS LINUS SYZBOT 	YES	NO	checked

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

ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 5
* Conservative score: 5. No floor or cap applied.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Strong corruption primitive. The race can make `ctrl->sqs` and `ctrl->cqs` arrays smaller than the later `max_qid` validation limit, allowing out-of-bounds access in queue handling.
* +1 Memory layout invariant restoration. The patch restores consistency between allocation size and later queue-id validation by copying `max_qid` into `ctrl->max_qid`.
* +1 Reliable kernel crash / strong DoS. The commit explicitly mentions KASAN out-of-bounds warning and potential memory corruption.
* +1 Important storage path. This is in NVMe target controller and queue management, a security-relevant storage subsystem path.

Paranoid additional signal:

* +1 Weak exploitation concern. The out-of-bounds condition affects active kernel pointer arrays for NVMe queues, and the later queue ID can select entries beyond the allocated array. This supports manual review beyond crash-only handling, but does not prove arbitrary write or LPE.

Non-awarded signals:

* RealUAF not awarded. This is a race-driven OOB array access, not a use-after-free.
* Concrete repeated release/refcount not awarded. No second lifetime mutation on the same dangling reference is shown.
* Controlled reclaim not demonstrated.
* Arbitrary or directed kernel write not demonstrated.
* Confidentiality and integrity are not directly awarded as separate ActionableScore points because no leak, credential overwrite, or protected-object modification is proven.
* Direct remote reachability not awarded. A remote NVMe initiator alone normally cannot modify `max_qid`.
* Race penalty not applied. The bug is a race, but supplied evidence does not prove a narrow one-shot or externally uncontrollable timing condition.
* Host-admin penalty not applied. NVMe target configfs management is typically administrative, but the supplied evidence does not fully resolve whether the complete trigger is host-admin-only versus delegated storage management.

3. Reachability analysis

The trigger requires a race between changing a subsystem `max_qid` value through nvmet configfs and allocating a new controller in `nvmet_alloc_ctrl()`. After the controller allocates queue arrays using the old smaller value, later queue validation can observe the new larger subsystem value and accept queue IDs beyond the allocated arrays.

A remote NVMe initiator may participate in controller creation and later queue creation, but the remote initiator alone is not shown to be able to change `max_qid`. The configuration-changing actor is local control plane userspace. In typical deployments this is host administrator or a storage management service, but delegated or reduced-capability management is plausible and not fully resolved from the supplied input.

Namespace-scoped privilege is not established. The nvmet configfs control path is not shown to be fully usable from attacker-created namespaces. Prior setup of an NVMe target subsystem is required for practical exposure. No rare hardware requirement is established for the generic nvmet target path. The race appears repeatable by repeatedly modifying `max_qid` and creating controllers, so no hard-race penalty is applied.

4. Primitive and severity interpretation

The exact primitive is an out-of-bounds access to controller queue pointer arrays caused by an allocation-size versus validation-limit mismatch. The arrays are allocated using one `max_qid` value, while later validation can use a larger changed value from the subsystem. This can let queue installation or validation operate beyond the allocated `sqs` or `cqs` arrays.

This is not fixed stale storage and not a UAF. It is active kernel state associated with a live NVMe target controller. The demonstrated consequence is KASAN OOB warning and likely kernel crash or memory corruption. The speculative consequence is stronger exploitation through heap corruption, but controlled reclaim, arbitrary write, credential overwrite, or a demonstrated privilege escalation path is not established.

PrimitiveClass is CLASS_A because an attacker-influenced OOB kernel heap access/write candidate is directly established by the patch context. ImportantCandidate is YES because concrete kernel memory corruption exists and the privilege boundary is not fully resolved. AutoDowngradeAllowed is NO because automatically closing this as ordinary Moderate would discard a real kernel OOB corruption primitive in an important storage target path.

5. One-sentence report phrase

A race between nvmet configfs `max_qid` updates and controller allocation can leave NVMe target queue arrays allocated with an old smaller size while later queue validation accepts larger queue IDs, causing out-of-bounds kernel heap access and requiring manual review for possible impact beyond DoS.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: concrete OOB kernel memory corruption is established, the affected objects are active NVMe target queue structures, and the exact practical privilege boundary is unresolved.

7. Call-site confidence

Call-site confidence: high

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

Patch: nvmet: fix max_qid race between configfs and controller allocation [ Upstream
Commit: 2c23fc91789dfd9db746edb3ae9b90d65fabd410
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2c23fc91789dfd9db746edb3ae9b90d65fabd410

Changed files:
  drivers/nvme/target/admin-cmd.c
  drivers/nvme/target/core.c
  drivers/nvme/target/fabrics-cmd.c
  drivers/nvme/target/nvmet.h
  drivers/nvme/target/pci-epf.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=2c23fc91789dfd9db746edb3ae9b90d65fabd410

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

The original Linux kernel CVE announcement for CVE-2026-90206 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-90206

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 5
  Paranoid ActionableScore: 6

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: IMPORTANT
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): IMPORTANT

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).