[CVE-2026-53372][MODERATE REGULAR] iommu/vt-d: Block PASID attachment to nested domain with dirty tracking

[CVE-2026-53372][MODERATE REGULAR] iommu/vt-d: Block PASID attachment to nested domain with dirty tracking

[AL-KERNEL]

CVE: CVE-2026-53372
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: iommu/vt-d: Block PASID attachment to nested domain with dirty tracking
Commit: 3ea9ce757bd3de955b56e7bc5672fc479e40b045
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ea9ce757bd3de955b56e7bc5672fc479e40b045
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53372
Analysis date: Sun, 19 Jul 2026 05:55:23 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Borderline, manual review recommended
Manual review required: YES

Summary:
Intel VT-d nested PASID attachment could be allowed while dirty tracking was enabled, causing DMA-written guest pages to be missed during migration or snapshot workflows and potentially corrupting migrated VM state.

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

The original Linux kernel CVE announcement for CVE-2026-53372 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53372

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-2026-53372	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N';CWE-754;CWE-703;CWE-345;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L';BEST CVSS score: '5.5';DESCR 'Intel VT-d allowed PASID attachment to a nested IOMMU domain even when the stage 2 parent domain had dirty tracking configured. The kernel does not support dirty tracking for this nested PASID configuration, so DMA writes may be missed in the dirty bitmap and dirty guest pages may be lost during migration or snapshot style workflows. For the CVSS the PR:L is used in the paranoid score because a delegated VM management service or reduced capability virtualization role may be able to request PASID attachment and dirty tracking without full host administrator control. The issue is not directly network reachable and does not indicate host memory corruption. Impact is mainly integrity loss for migrated VM state or workload data rather than direct host privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3)	YES	SIMPLEFIX HARDWARE MEMORY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	YES	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Borderline, manual review recommended**

## 2. Signal breakdown

Conservative signals:

* Integrity impact plausible: +1
  Dirty pages may be missed when PASID is attached to a nested domain with dirty tracking enabled, causing migration or snapshot state loss.
* Availability impact realistic: +1
  Lost dirty pages can make a migrated VM or workload inconsistent or unusable, though this is not a direct host crash.
* Privileged DMA/IOMMU state-management issue: +1
  The bug affects IOMMU nested domain and PASID handling, which controls DMA-visible memory translation and dirty tracking semantics.
* Requires admin or equivalent virtualization/device-management privileges in typical deployments: -2
  Triggering normally requires VFIO/IOMMUFD or VM device-assignment control, not ordinary local user access.
* Net result: 1 to 2 range. Rounded to 2 because the affected state is migration-relevant and not just cosmetic bookkeeping.

Paranoid signals:

* Same integrity and availability concerns: +2
* DMA/IOMMU dirty-tracking state issue: +1
* Reduced-privilege virtualization role may trigger it: +0 instead of -2
  In cloud or delegated virtualization setups, a VM management service, reduced-capability root, or tenant-controlled device-assignment path may be able to request this configuration without full host-root equivalence.
* Rare configuration dependency: -1
  Requires Intel VT-d nested domains, PASID, and dirty tracking together.
* Net paranoid score: 3

No memory corruption, UAF, OOB write, arbitrary write, or host privilege-escalation primitive is shown by the patch.

## 3. Reachability analysis

The bug is local/control-plane reachable through IOMMU nested domain PASID attachment, typically via privileged virtualization or device-assignment management paths. It is not network reachable by itself. Namespaces or containers do not automatically make this unprivileged, but delegated VM-management roles or reduced-capability service accounts can lower the practical privilege barrier in some deployments. The affected configuration is specialized: Intel VT-d with nested translation, PASID attachment, and dirty tracking enabled, most relevant to VM migration or snapshot workflows.

## 4. Severity interpretation

This behaves more like a borderline actionable Moderate than an Important-class kernel memory corruption issue. The realistic impact is loss of migration integrity because dirty DMA-written pages may not be tracked and copied. Theoretical impact is serious for VM state correctness, but the patch does not support host memory corruption, direct LPE, information disclosure, or remote triggering.

## 5. One-sentence report phrase

Intel VT-d nested PASID attachment could be allowed while dirty tracking was enabled, causing DMA-written guest pages to be missed during migration or snapshot workflows and potentially corrupting migrated VM state.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Reason: this is not a strong Important candidate because there is no demonstrated memory corruption or LPE primitive, but it affects IOMMU dirty tracking and VM migration integrity, so it should not be blindly auto-closed without checking whether the product exposes delegated virtualization or device-assignment workflows.

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

Patch: iommu/vt-d: Block PASID attachment to nested domain with dirty tracking
Commit: 3ea9ce757bd3de955b56e7bc5672fc479e40b045
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3ea9ce757bd3de955b56e7bc5672fc479e40b045

Commit description:

Kernel lacks dirty tracking support on nested domain attached to PASID,
fails the attachment early if nesting parent domain is dirty tracking
configured, otherwise dirty pages would be lost.

Cc: stable@vger.kernel.org
Fixes: 67f6f56 ("iommu/vt-d: Add set_dev_pasid callback for nested domain")
Suggested-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Link: https://lore.kernel.org/r/20260330101108.12594-2-zhenzhong.duan@intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Fixes: 67f6f56 ("iommu/vt-d: Add set_dev_pasid callback for nested  domain")
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/iommu/intel/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=3ea9ce757bd3de955b56e7bc5672fc479e40b045

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

The original Linux kernel CVE announcement for CVE-2026-53372 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53372

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:L/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
  The Best / paranoid CVSS score: 5.5

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: 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).