[CVE-2026-98282][MODERATE 7.0] powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba [ Upstream

[CVE-2026-98282][MODERATE 7.0] powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98282
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba [ Upstream
Commit: 98d8dcc4ebd10523507d4478e148809a7771a213
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=98d8dcc4ebd10523507d4478e148809a7771a213
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98282
Analysis date: Sat, 10 Oct 2026 18:11:04 -0400
ActionableScore: 5
ActionableScore lower bound: 4
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-2026-98282 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98282

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.

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

CVE-2026-98282	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98282 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=MODERATE_KPANIC RESULT=SAME (legacy and Aegis reconciliation agree; 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-190;*CWE-20;*CWE-787;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'An incomplete bounds check in iommu_tce_check_ioba validates only the first TCE entry and ignores the full range requested through npages. A multi page H_STUFF_TCE or H_PUT_TCE_INDIRECT operation can therefore pass validation even when the requested range extends beyond the IOMMU table, and arithmetic wraparound can also bypass the old upper bound check. This creates a plausible out of bounds TCE operation that may corrupt IOMMU mapping state, expose incorrectly mapped memory, or crash the host. For the CVSS the PR:L value is selected because exploitation requires control of a guest or access to a delegated KVM or VFIO context, but does not necessarily require full administrative privileges on the host. The issue is not directly network reachable. Impact is at least denial of service and may include confidentiality and integrity impact if the invalid TCE range affects host mappings or adjacent table state.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	MAYBE	SIMPLEFIX HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4	-	-	checked

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

ActionableScore=5
ActionableScoreLower=4
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 conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* No floor or cap was applied.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Strong corruption primitive. The old validation accepts a multi-entry TCE write range when only its first entry is inside the table. `H_STUFF_TCE` and `H_PUT_TCE_INDIRECT` are write-oriented operations, and both `ioba` and `npages` influence the invalid range.
* +1 Privileged kernel/device-management corruption path. The affected state is an IOMMU TCE table used for DMA translation, not passive diagnostic metadata.
* +1 Below-host-admin guest trigger. A malicious PowerPC KVM guest can supply the hypercall range without possessing host-administrator authority.

Paranoid signal:

* +1 Integrity plausible. An out-of-range TCE operation can modify translation state outside the intended table. The exact adjacent target and resulting host effect still require call-site review.

Not awarded:

* No UAF, controlled reclaim, callback influence, arbitrary target, or arbitrary kernel write is established.
* No confidentiality point because exposure of host memory through a resulting DMA mapping is not demonstrated.
* No crash point because the supplied evidence does not establish a kernel panic or reliable host failure.
* No LPE or guest escape point because later consumption of the corrupted state is not shown.
* No remote-network point because this is a KVM guest/VMM interface, not a direct network path.
* B5-R is not established. There is no retry-accumulated index, missing retry reset, or demonstrated later consumption of retry-corrupted state.
* B3-PENDING and B4-PENDING do not apply. There is no shared-backing write or authorization decision bypass.

3. Reachability analysis

The relevant attacker is primarily malicious guest code invoking `H_STUFF_TCE` or `H_PUT_TCE_INDIRECT`. The guest controls the requested IOBA range and page count, while the host VMM creates the VM and its TCE facilities. The vulnerable range operation itself does not require host UID 0 or host-administrator powers once the affected virtual IOMMU configuration is exposed to the guest.

A local VMM process with `/dev/kvm` access is a separate possible actor. Host administration may be needed to provision the VM or assigned device initially, but that prior provisioning is not the same as requiring host-admin authority for each guest trigger.

No user-namespace or network-namespace capability is involved. The path is PowerPC KVM specific, but architecture specificity alone does not justify a rare-hardware penalty. This is deterministic bounds validation rather than a timing race.

4. Primitive and severity interpretation

The exact primitive is acceptance of a multi-page TCE write range extending beyond the table capacity, including a possible unsigned arithmetic wraparound. This is active IOMMU translation state rather than fixed stale storage, and it is not a cleanup or destructor issue.

The primitive is classified as CLASS_A because the affected callers perform attacker-influenced multi-entry TCE write operations and the missing check permits those operations to exceed the validated table range. However, the supplied patch does not expose the full storage layout or subsequent consumers, so it does not establish arbitrary host memory access, controlled guest escape, or privilege escalation.

The demonstrated issue is stronger than validation-only bookkeeping because the rejected range is used by write-oriented TCE operations. The practical high-impact consequence remains unresolved because the exact out-of-range destination and later use are not visible. ImportantCandidate is therefore YES and automatic downgrade is unsafe, but the evidence supports Actionable Moderate rather than a proven high-end Important vulnerability.

5. One-sentence report phrase

An incomplete PowerPC IOMMU bounds check allows guest-controlled multi-page TCE operations to extend beyond the intended table range, creating an unresolved host translation-state corruption primitive that requires manual review.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Inspect the complete `H_STUFF_TCE` and `H_PUT_TCE_INDIRECT` call paths, the concrete TCE storage backend, downstream bounds checks, adjacent objects, and whether invalid entries are later consumed by hardware or host kernel translation walkers.

7. Call-site confidence

Call-site confidence: medium

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

Patch: powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba [ Upstream
Commit: 98d8dcc4ebd10523507d4478e148809a7771a213
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=98d8dcc4ebd10523507d4478e148809a7771a213

Changed files:
  arch/powerpc/kernel/iommu.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=98d8dcc4ebd10523507d4478e148809a7771a213

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

The original Linux kernel CVE announcement for CVE-2026-98282 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98282

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: 4
  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).