[CVE-2026-98833][MODERATE 7.0] mtd: core: call _get_device() with the master MTD [ Upstream

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

CVE: CVE-2026-98833
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: mtd: core: call _get_device() with the master MTD [ Upstream
Commit: 95c8f36293c22d450c371167ad4f9a5bbadc7539
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95c8f36293c22d450c371167ad4f9a5bbadc7539
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98833
Analysis date: Sat, 24 Oct 2026 11:42:43 -0400
ActionableScore: 5
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Opening an affected gluebi partition can make the master callback derive a bogus `gluebi_device` and write outside the intended heap object.

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

The original Linux kernel CVE announcement for CVE-2026-98833 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98833

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 7.0
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-2026-98833	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98833 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-843;*CWE-787;CWE-125;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR '__get_mtd_device passed a partition mtd_info to the master _get_device callback even though gluebi_get_device assumes that the argument is the embedded master MTD and applies container_of to it. For gluebi partitions this produces an invalid gluebi_device address and subsequent field reads or writes can cause a kernel crash or corrupt a neighboring kernel object. For the CVSS the PR:L value reflects that a local process must be able to access the affected MTD device, while device permissions and the required gluebi partition configuration reduce practical exposure. The base impact is CIA:LLH because invalid object reads and writes are present but disclosure or escalation is not demonstrated. The paranoid impact is CIA:HHH because the wrong object write is a concrete memory corruption primitive that requires manual layout and exploitability analysis. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7.8 and the production ActionableScore returned 5 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the ActionableScore threshold rule was applied. 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 has no review artifact for this run. Exact triggered rule markers were INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4. The independent weaker Aegis shadow evaluated CVSS 2.6 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	SIMPLEFIX LINUS  KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4	-	-	checked

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

ActionableScore=5
PrimitiveClass=CLASS_A
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 3.
* Conservative score: 5. Applied Important-primitive preservation floor: 3 -> 5.
* Raw paranoid score: 3.
* Paranoid score: 5. Same floor; no speculative exploit bonus.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +2 — Confirmed attacker-triggered heap OOB/wrong-object write: a partition `mtd_info` is passed where `gluebi_get_device()` requires the embedded master object; `container_of()` consequently derives an invalid `gluebi_device`, and supplied evidence confirms subsequent field writes.
* +1 — Kernel crash/strong DoS is plausible from invalid structured-object accesses.
* -0 — Device access and gluebi partition configuration constrain exposure, but do not prove host-admin-equivalent trigger privileges or justify a numeric penalty.
* Floor to 5 — The concrete heap OOB write into a wrongly derived kernel object is an Important-preserving corruption primitive requiring layout and downstream-consumer review.

No arbitrary target/payload, controlled reclaim, disclosure, LPE, or protected neighboring victim is shown. No extra availability point is awarded for the same crash. NEW52/B5-R does not apply: there is no retry-accumulated index. B3-PENDING and B4-PENDING do not apply.

3. Reachability analysis

The affected configuration requires gluebi plus an MTD partition, likely provisioned beforehand by a privileged administrator. The supplied summary grounds a later local process with permission to access the MTD device as the trigger; that process need not retain host-administrator powers or UID 0. MTD access is not user-namespace capability scoped. Exact device ACLs and configuration prevalence remain deployment-dependent, but no race, retry loop, or special hardware timing is shown.

4. Primitive and severity reading

The primitive is a non-UAF heap wrong-object/OOB write caused by applying `container_of()` to a partition object as though it were the master’s embedded `mtd_info`. It is CLASS_A because a concrete attacker-invoked kernel write outside the intended object is evidenced; arbitrary write and exploit completion are not. Crash and neighboring-object corruption are supported, while confidentiality, privilege escalation, and controlled object takeover remain unproven. Auto-downgrade is unsafe pending review of exact written fields, allocation adjacency, and later consumption.

5. One-sentence report phrase

Opening an affected gluebi partition can make the master callback derive a bogus `gluebi_device` and write outside the intended heap object.

6. Manual review advice

MANUAL CHECK REQUIRED

Review the exact gluebi fields written, allocator layout, reachable partition-open permissions, and whether corrupted adjacent state is subsequently consumed.

7. Call-site confidence

Call-site confidence: medium

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

Patch: mtd: core: call _get_device() with the master MTD [ Upstream
Commit: 95c8f36293c22d450c371167ad4f9a5bbadc7539
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95c8f36293c22d450c371167ad4f9a5bbadc7539

Changed files:
  drivers/mtd/mtdcore.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=95c8f36293c22d450c371167ad4f9a5bbadc7539

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

The original Linux kernel CVE announcement for CVE-2026-98833 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98833

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:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 5

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: YES
Published priority for this report (same as in Subject): MODERATE 7.0

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).