[CVE-2026-98723][IMPORTANT] nvmet: copy the hostid into the ctrl before creating PR pc_refs [ Upstream

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

CVE: CVE-2026-98723
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: NO
Patch: nvmet: copy the hostid into the ctrl before creating PR pc_refs [ Upstream
Commit: d3d6d7efdacc08616d23b3ac42272a494951dc0f
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d3d6d7efdacc08616d23b3ac42272a494951dc0f
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98723
Analysis date: Sat, 24 Oct 2026 02:47:42 -0400
ActionableScore: 7
ActionableScore lower bound: unknown
Actionable bucket: Strong Important candidate
Manual review required: YES

Summary:
An authorized NVMe host can successfully preempt a registrant while the target fails to abort and drain that victim’s in-flight I/O, violating persistent-reservation fencing.

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

The original Linux kernel CVE announcement for CVE-2026-98723 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98723

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.

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AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-98723	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-98723 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=3 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H';CWE-665;CWE-863;Other CVSS 'AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '7.3';DESCR 'This is an initialization ordering and reservation enforcement flaw in the NVMe target. nvmet_ctrl_init_pr snapshots ctrl hostid into each per controller namespace pc_ref before the real hostid is copied from the connection data, so the stored value is the nil UUID. During Persistent Reservation Preempt and Abort, nvmet_pr_set_ctrl_to_abort cannot match the displaced registrant and therefore does not kill or drain its in flight I/O even though the preempting host receives success. The affected path requires persistent reservations and a namespace that exists before the controller connects, which also covers reconnects. For the CVSS the PR:L value reflects that the attacker must be an authorized NVMe host able to connect to the target and issue reservation commands. Continued victim I/O can violate storage fencing and may cause stale writes, data consistency damage, or service disruption across hosts sharing the namespace. There is no evidence of kernel memory corruption, information disclosure, or direct code execution. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 7.3 and the production ActionableScore returned 7 with recommendation Strong Important candidate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to MODERATE_KPANIC because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to IMPORTANT because the ActionableScore threshold rule was applied. KP and FD specialist checks stage IMPORTANT to IMPORTANT because a specific evidence based protection or manual review veto was applied. final reconciliation stage IMPORTANT to IMPORTANT because KP specialist did not establish a qualifying panic. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS and INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 and V59_LEGACY_CLASSA_KP_VETO and MANUAL_REVIEW_REQUIRED and TEMP_KPANIC_MERGE_IMPORTANT_WINS and KPANIC_UNSUPPORTED_REMOVED. The independent weaker Aegis shadow evaluated CVSS 3.5 and ActionableScore 3 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate (with actual score 7)	MAYBE	INIT NVME IMPROVEONLY DEBUGFS LINUS INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 V59_LEGACY_CLASSA_KP_VETO MANUAL_REVIEW_REQUIRED TEMP_KPANIC_MERGE_IMPORTANT_WINS KPANIC_UNSUPPORTED_REMOVED	-	-	checked

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

ActionableScore=7
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=CONFIRMED
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 7.
* Conservative score: 7; no floor or cap applied.
* Raw paranoid score: 7.
* Paranoid score: 7; no additional speculative effects scored.
* Final recommended bucket: **Strong Important candidate**::

2. Signal breakdown

* +2 — Network-reachable storage-policy bypass: an authorized NVMe host can invoke Persistent Reservation Preempt and Abort against the target.
* +2 — Material security-boundary/policy failure: the nil `pc_ref->hostid` prevents identification, killing, and draining of the displaced registrant’s in-flight I/O.
* +1 — Practical chain: connect snapshots the nil UUID, reservation preemption later fails the host-ID match, and the command reports success while victim I/O continues.
* +1 — Integrity plausible: continued victim writes can violate reservation fencing and alter shared namespace data after successful preemption.
* +1 — Important storage path: this affects NVMe persistent reservations and multi-host shared-storage consistency.
* No UAF, OOB access, arbitrary write, kernel-memory corruption, disclosure, LPE, or proven kernel crash is shown.
* No extra availability point: service disruption is plausible, but no distinct reliable target-host crash or persistent outage is established.

3. Reachability analysis

The grounded attacker is an authorized NVMe fabric host able to connect and issue reservation commands, not an ordinary unauthenticated network peer. This is below effective target-host administration and does not require target-host UID 0. Persistent reservations, a pre-existing namespace, and host authorization are required service configuration; reconnects are explicitly affected. Linux user/net namespace capabilities are not part of the shown trigger.

4. Primitive and severity reading

The primitive is an initialization-ordering failure in active reservation identity state. `nvmet_ctrl_init_pr()` snapshots a zero host ID before the connection host ID is copied; its sole later consumer therefore fails to abort and drain the preempted host’s I/O. This is CLASS_A storage-fencing/policy bypass, not memory corruption.

`AuthorizationDecisionBypass=NO` and B4 is not confirmed because the patch does not show a conventional authorization guard changing a command from DENY to ALLOW; it shows failure to enforce the post-admission abort/drain semantics. The protected namespace and fencing impact are nevertheless concrete. Data corruption and disruption are plausible, while specific stale writes or permanent damage are not guaranteed.

5. One-sentence report phrase

An authorized NVMe host can successfully preempt a registrant while the target fails to abort and drain that victim’s in-flight I/O, violating persistent-reservation fencing.

6. Manual review advice

MANUAL CHECK REQUIRED

The confirmed cross-host storage-fencing failure has material integrity implications and must not be auto-downgraded despite the absence of kernel memory corruption or LPE.

7. Call-site confidence

Call-site confidence: high

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

Patch: nvmet: copy the hostid into the ctrl before creating PR pc_refs [ Upstream
Commit: d3d6d7efdacc08616d23b3ac42272a494951dc0f
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d3d6d7efdacc08616d23b3ac42272a494951dc0f

Changed files:
  drivers/nvme/target/core.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=d3d6d7efdacc08616d23b3ac42272a494951dc0f

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

The original Linux kernel CVE announcement for CVE-2026-98723 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98723

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:A/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
  The Best / paranoid CVSS vector: AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
  The Best / paranoid CVSS score: 7.3

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: 7

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).