[CVE-2026-98634][MODERATE REGULAR] scsi: sd_zbc: Reject disks with too many zones [ Upstream

[CVE-2026-98634][MODERATE REGULAR] scsi: sd_zbc: Reject disks with too many zones [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98634
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: scsi: sd_zbc: Reject disks with too many zones [ Upstream
Commit: d8791ae55d85dfaeafa20ea48365482a0cc5a107
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d8791ae55d85dfaeafa20ea48365482a0cc5a107
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98634
Analysis date: Fri, 23 Oct 2026 21:07:01 -0400
ActionableScore: 2
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A malicious or artificial zoned SCSI device can cause zone-count truncation and signed index overflow, producing inconsistent per-zone resource sizing, but a concrete out-of-bounds write or stronger security consequence is not established by the supplied patch.

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

The original Linux kernel CVE announcement for CVE-2026-98634 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98634

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: NO

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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

CVE-2026-98634	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98634 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE RESULT=DIFF (final Legacy and Aegis differ; FINAL: MODERATE, Aegis: MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';CWE-190;CWE-681;CWE-131;*CWE-787;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7.5';DESCR 'The SCSI zoned block code computes the number of zones with 64 bit arithmetic but previously stored the result in an unsigned int. A device reporting more zones than the destination type can represent may therefore cause a truncated zone count to be used for per zone resource sizing while later REPORT ZONES processing can still observe a larger count. The signed zone_idx counter can also overflow after INT_MAX zones. This creates inconsistent bookkeeping and a plausible risk of out of bounds access if later code indexes resources sized from the truncated count. The directly established impact is denial of service during device discovery or zone processing. The worst case impact may include kernel memory corruption if the size mismatch reaches a per zone array access and therefore confidentiality and integrity impact cannot be excluded without a complete consumer audit. For the CVSS the PR:N value is used because an attacker controlling a physical SCSI device or an already connected storage target does not require an account or privileges on the victim host. The base attack vector is physical. The paranoid attack vector is adjacent because the same device behavior may be supplied through iSCSI or another reachable storage fabric when the attacker controls the target. Exploitation requires an artificial device reporting more than INT_MAX zones and is not realistic for normal storage media. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 7.5 and the production ActionableScore returned 2 with recommendation Ordinary Moderate. 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 MODERATE because the ActionableScore threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS and DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is MODERATE.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	MAYBE	SIMPLEFIX HARDWARE LINUS  INCREASED_TO_MODERATE7_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=2
ActionableScoreLower=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 2
* Paranoid score: 2
* No floor or cap was applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Weak or indirect corruption candidate. A 64-bit zone count is truncated before it is used to size per-zone resources, while the device may report more zones.
* +1 Important storage path. The inconsistent value affects SCSI zoned-device resource sizing and zone enumeration.
* -1 Rare and difficult input condition. The device must expose more than INT_MAX zones, which the commit explicitly describes as unrealistic for existing media.
* Total: 1.

Paranoid signals:

* +1 Weak or indirect corruption candidate.
* +1 Important storage path.
* The rarity penalty is withheld because an emulated or malicious storage target could theoretically fabricate the reported capacity and zone geometry without corresponding real media.
* Total: 2.

Not awarded:

* No confirmed heap or slab OOB write is shown.
* No concrete destination, write width, corrupted adjacent object, or later consumption of corrupted memory is established.
* No reliable kernel crash is documented.
* No UAF, controlled reclaim, arbitrary write, disclosure, authorization bypass, or privilege escalation is established.
* NEW52 B5-R does not apply. There is no retry-accumulated index, no missing retry reset, and no confirmed OOB write followed by consumption of corrupted structured state.
* Confidentiality and integrity points are not awarded from the bookkeeping mismatch alone.

3. Reachability analysis

The malformed values originate from a zoned SCSI device during scanning. A malicious physical device or a controlled SCSI target could potentially supply artificial capacity and zone geometry, but the supplied evidence does not establish a concrete iSCSI or other network trigger.

The complete privilege boundary is unresolved. Physical attachment may require no host account, while creating or attaching an emulated storage target may require prior administrative configuration. Therefore HostAdminRequired remains UNKNOWN. No user-namespace or network-namespace capability path is shown. There is no race or timing requirement.

4. Primitive and severity interpretation

The established defect is integer truncation plus signed-counter overflow producing inconsistent zone bookkeeping. The count can be smaller than the number of zones subsequently reported, creating a credible but unconfirmed risk that a later per-zone consumer could index beyond an allocated resource.

This remains CLASS_C because the supplied patch and context do not show the actual downstream memory access needed to establish an OOB write. The demonstrated consequence is rejection-worthy invalid device state. Kernel crash or memory corruption remains a hypothesis requiring examination of allocations and consumers derived from early_zone_info.nr_zones and zone_idx.

ImportantCandidate is NO because none of the required B5-R mechanics or another Important-preserving primitive is established. AutoDowngradeAllowed is YES because the current evidence supports invalid-state and potential DoS behavior rather than confirmed corruption. Manual review is still recommended because the allocation-versus-reported-count mismatch could conceal a downstream OOB operation not visible in this patch.

5. One-sentence report phrase

A malicious or artificial zoned SCSI device can cause zone-count truncation and signed index overflow, producing inconsistent per-zone resource sizing, but a concrete out-of-bounds write or stronger security consequence is not established by the supplied patch.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Trace every allocation and array access derived from early_zone_info.nr_zones, and inspect whether sd_zbc_report_zones can process a zone index beyond those allocations before rejecting or terminating enumeration.

7. Call-site confidence

Call-site confidence: medium

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

Patch: scsi: sd_zbc: Reject disks with too many zones [ Upstream
Commit: d8791ae55d85dfaeafa20ea48365482a0cc5a107
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d8791ae55d85dfaeafa20ea48365482a0cc5a107

Changed files:
  drivers/scsi/sd_zbc.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=d8791ae55d85dfaeafa20ea48365482a0cc5a107

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

The original Linux kernel CVE announcement for CVE-2026-98634 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98634

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:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.5

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: 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: 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).