[CVE-2026-99086][MODERATE REGULAR] dm-integrity: validate the superblock on resume [ Upstream

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

CVE: CVE-2026-99086
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dm-integrity: validate the superblock on resume [ Upstream
Commit: 454b67fcc28c18502e47dfb9f067b04c28628ada
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=454b67fcc28c18502e47dfb9f067b04c28628ada
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99086
Analysis date: Mon, 26 Oct 2026 20:32:09 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A host storage administrator can change dm-integrity geometry while suspended, causing an invalid journal-page lookup and a 512-byte NULL-pointer write on resume.

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

The original Linux kernel CVE announcement for CVE-2026-99086 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99086

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.

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

CVE-2026-99086	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-99086 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:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H';*CWE-20;CWE-129;*CWE-787;**CWE-476;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.6';DESCR 'dm_integrity_resume accepted a newly read superblock lacking checking whether its geometry still matched the structures allocated by the constructor. Increasing log2_sectors_per_block while the target was suspended could make access_journal_data index beyond the journal page array and then perform a 512 byte write through an invalid pointer returned by lowmem_page_address. The demonstrated result is a NULL pointer write and kernel crash. An out of bounds page lookup also creates a limited memory corruption concern if a non NULL value is consumed as a page pointer, although the patch does not establish a controlled arbitrary write or practical privilege escalation. For the CVSS the PR:H value is used because reliable triggering normally requires permission to suspend and resume the dm target and modify its underlying block device. The issue is local and is not directly reachable through ordinary network traffic. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.6 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were 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 DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V41_INHERITED_KPANIC_PROMOTION_BLOCKED and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.3 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 1)	MAYBE	READ DANGER DISK NOMEMCHK LOG HARDWARE LINUS SYZBOT  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 V41_INHERITED_KPANIC_PROMOTION_BLOCKED MANUAL_REVIEW_REQUIRED	-	-	checked

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

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

1. ActionableScore

* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; a stronger non-NULL destination is possible but not sufficiently established for another point.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 constrained/indirect kernel overwrite: attacker-modified geometry causes an out-of-range journal-page lookup followed by a 512-byte write through the resulting invalid page pointer.
* +1 reliable kernel crash/strong DoS: the documented path obtains NULL and writes through `lowmem_page_address(NULL)`, plausibly faulting the kernel.
* +1 important storage-integrity path: the mismatch affects dm-integrity journal geometry and journal writes.
* -2 proven host-administrator-equivalent prerequisite: completing the demonstrated sequence requires suspending/resuming the device-mapper target and modifying its underlying block device.

Not awarded: controlled destination or payload, arbitrary write, controlled reclaim, disclosure, protected-data corruption, LPE, or additional availability impact. The out-of-range operation is initially a page-array read; the demonstrated subsequent write is through NULL, not a confirmed heap/slab OOB write into an identified adjacent object. NEW52 B5-R does not apply because no retry-accumulated index is involved.

3. Reachability analysis

The complete trigger requires control of both dm-integrity lifecycle operations and the underlying block device. These are host storage-administration operations, not an ordinary user or namespace-local capability path. No attacker-created user namespace, delegated device access, remote path, special hardware, race, or retry sequence is shown. Numeric UID 0 is not independently required if equivalent host capabilities are held, hence `RequiresHostUID0=UNKNOWN`.

4. Primitive and severity reading

The primitive is an attacker-influenced geometry mismatch causing an OOB page-pointer lookup and a fixed 512-byte write through the resulting invalid pointer. It is CLASS_B because a real invalid kernel write exists, but the proven destination is NULL and useful corruption of a non-NULL target remains unresolved. This is neither a UAF nor an authorization bypass. Host-admin-only triggering, immediate crash behavior, and lack of a demonstrated useful target make it unsuitable as an Important candidate; automatic downgrade remains permissible.

5. One-sentence report phrase

A host storage administrator can change dm-integrity geometry while suspended, causing an invalid journal-page lookup and a 512-byte NULL-pointer write on resume.

6. Manual review advice

MANUAL CHECK RECOMMENDED

Confirm whether any reachable index can fetch a non-NULL value that survives `lowmem_page_address()` and produces corruption before faulting.

7. Call-site confidence

Call-site confidence: high

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

Patch: dm-integrity: validate the superblock on resume [ Upstream
Commit: 454b67fcc28c18502e47dfb9f067b04c28628ada
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=454b67fcc28c18502e47dfb9f067b04c28628ada

Changed files:
  drivers/md/dm-integrity.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=454b67fcc28c18502e47dfb9f067b04c28628ada

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

The original Linux kernel CVE announcement for CVE-2026-99086 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99086

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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.6

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: 1

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).