[CVE-2026-98002][MODERATE REGULAR] iommu/amd: Fix ineffective error check in nested domain allocation [ Upstream

[CVE-2026-98002][MODERATE REGULAR] iommu/amd: Fix ineffective error check in nested domain allocation [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98002
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: iommu/amd: Fix ineffective error check in nested domain allocation [ Upstream
Commit: 80c231f5577229d1e90a1e312b3095f9502f8625
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80c231f5577229d1e90a1e312b3095f9502f8625
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98002
Analysis date: Sat, 26 Sep 2026 15:48:23 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline / manual review recommended
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-98002 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98002

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: YES

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

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

CVE-2026-98002	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98002 CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';CWE-195;CWE-252;CWE-754;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.8';DESCR 'An error from amd_iommu_pdom_id_alloc can be converted from a negative int into a large positive u32 before it is checked. This allows nested domain setup to continue with a host domain ID that was never allocated when the ID space is exhausted or memory allocation fails. For the CVSS the PR:L value is used because triggering requires a local process with access to iommufd or a delegated virtualization interface, but it does not necessarily require unrestricted host administrator privileges. AC:H reflects the need to reach an allocation failure condition. The issue is not network reachable. The direct impact is incorrect nested IOMMU domain setup and possible loss of availability. In the paranoid assessment an invalid host domain ID may also interfere with domain mapping, invalidation, or DMA isolation, giving a plausible but unconfirmed limited confidentiality and integrity impact. No concrete UAF, OOB write, or arbitrary write primitive is established by the supplied code.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline / manual review recommended (with actual score 3)  SKIP CVE-2026-98002 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES  NO NO unknown 	MAYBE	SIMPLEFIX TEST 	-	-	checked

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

ActionableScore=3
ActionableScoreLower=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2
* Raw paranoid score: 3
* Paranoid score: 3
* No floor or cap was applied.
* Final recommended bucket: **Borderline / manual review recommended**::

2. Signal breakdown

Conservative signals:

* +1 Weak or indirect corruption candidate. A negative allocator result is converted to a large unsigned value and accepted as a valid host domain ID.
* +1 Privileged kernel or device-management state corruption path. The invalid value becomes active AMD IOMMU nested-domain mapping state rather than remaining passive metadata.

Paranoid signal:

* +1 Weak exploitation concern. The invalid identifier selects a security-sensitive host IOMMU domain and could plausibly affect domain lookup, invalidation, or DMA isolation if downstream consumers truncate, alias, or otherwise accept it.

Not awarded:

* No UAF, stale lifetime access, OOB access, refcount corruption, or repeated release is established.
* No controlled identifier collision, arbitrary write, controlled reclaim, disclosure, or privilege escalation is demonstrated.
* No reliable kernel crash or host-wide DoS is established.
* No confidentiality or integrity points are awarded merely from the speculative possibility of DMA-isolation failure.
* No remote-reachability point is awarded.
* No privilege penalty is applied because host-admin-equivalent privilege is not positively established.
* No rare-hardware penalty is applied merely because AMD IOMMU nested translation is involved.

3. Reachability analysis

The vulnerable operation is local and reached through nested-domain allocation in iommufd or associated virtualization management. A local VMM or delegated device-management process is the likely actor, but the supplied code does not establish whether the complete sequence is available below host-admin privilege. It also does not establish that an attacker-created user namespace provides all required access, so both privilege fields remain UNKNOWN.

The error path requires exhaustion of the physical-domain ID space or memory pressure. This is a meaningful precondition, but no race or narrow timing window exists. The supplied context does not show whether an attacker can independently force that allocation failure. AMD IOMMU nested translation and prior virtualization or device-assignment setup are required, but the exact provisioning boundary is not visible.

4. Primitive and severity interpretation

The exact primitive is acceptance of an unallocated host domain ID caused by a signed-to-unsigned conversion before error checking. This creates invalid active IOMMU domain state, but it is not a lifetime violation and does not establish memory corruption.

PrimitiveClass is CLASS_C because the demonstrated behavior is invalid-state propagation without an independently useful read, write, reuse, or ownership primitive. A stronger consequence is technically possible if downstream code masks the value into a valid domain, indexes structures unsafely, or performs invalidation against the wrong domain, but none of those mechanisms is established here.

ImportantCandidate is NO because no Important-preserving primitive is demonstrated. AutoDowngradeAllowed is YES because the available evidence supports an invalid-state issue requiring follow-up rather than unresolved concrete kernel corruption. Operationally, this is a borderline issue whose downstream use sites should be checked before routine closure.

5. One-sentence report phrase

A signed allocation error can be accepted as a large host IOMMU domain ID, creating invalid nested-domain state with unresolved but unproven implications for domain invalidation and DMA isolation.

6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Trace all consumers of gdom_info->hdom_id and determine whether an out-of-range value can alias a valid hardware domain, index software state, target the wrong invalidation context, or weaken DMA isolation.

7. Call-site confidence

Call-site confidence: medium

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

Patch: iommu/amd: Fix ineffective error check in nested domain allocation [ Upstream
Commit: 80c231f5577229d1e90a1e312b3095f9502f8625
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=80c231f5577229d1e90a1e312b3095f9502f8625

Changed files:
  drivers/iommu/amd/nested.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=80c231f5577229d1e90a1e312b3095f9502f8625

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

The original Linux kernel CVE announcement for CVE-2026-98002 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98002

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:H/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS score: 5.8

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: 2
  Paranoid ActionableScore: 3

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).