[CVE-2026-53322][IMPORTANT] vfio/pci: Clean up DMABUFs before disabling function [ Upstream

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

CVE: CVE-2026-53322
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: vfio/pci: Clean up DMABUFs before disabling function [ Upstream
Commit: 4f1000a30f67cf7d328059242776a858611d5ef9
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4f1000a30f67cf7d328059242776a858611d5ef9
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53322
Analysis date: Fri, 26 Jun 2026 16:04:17 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
VFIO PCI could leave a stale DMABUF mapping to MMIO BAR resources during device shutdown, allowing local VFIO users to retain unintended access after function disable and possible BAR reuse by another driver.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-53322 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53322

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: IMPORTANT
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
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CVE-2026-53322	IMPORTANT	CHECK	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-672;CWE-362;CWE-284;*CWE-664;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'VFIO PCI DMABUF cleanup was performed after vfio_pci_core_disable, leaving a small shutdown window where MMIO BAR access through exported DMABUFs could remain possible after the function MSE was cleared. If the BAR resources are freed and later claimed by another driver, a stale DMABUF mapping may expose unintended MMIO access to resources that should no longer belong to the VFIO user. For the CVSS the PR:L is used because exploitation requires local access to an assigned VFIO PCI device or a process that can hold exported DMABUFs, not full host administrator privileges. The issue is not network reachable and is triggered through local VFIO device lifecycle operations. Impact is at least local denial of service or device state corruption, and in the paranoid case may include confidentiality and integrity impact through stale MMIO access to reused BAR resources. YES REQUIRES MANUAL CHECK';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)  SKIP CVE-2026-53322  SKIP The Fixes patch not applied yet, so unlikely that actual: 5d74781ebc86c5fa9e9d6934024c505412de9b52 YES  NO NO unknown 	MAYBE	UAF HARDWARE KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local low-privileged trigger: +1. A user or process with access to an assigned VFIO PCI device and exported DMABUFs can participate in the vulnerable lifecycle path.
* Real lifetime corruption: +1. DMABUF access can outlive the expected BAR accessibility window during device shutdown.
* Privileged kernel/device-management resource lifetime path: +1. The bug is in VFIO PCI teardown and BAR/MMIO resource management.
* Confidentiality impact plausible: +1. Stale MMIO access could expose resources after ownership changes.
* Integrity impact plausible: +1. Stale MMIO access could potentially modify device/MMIO state that no longer belongs to the VFIO user.
* Hard or tiny timing window: -1. The commit explicitly describes a tiny window.
* Rare/configuration-dependent exposure: -1. Requires VFIO PCI DMABUF export support and a suitable device assignment setup.
* Cross-boundary resource ownership concern: +1. The stale mapping may cross from an old VFIO user into resources later claimed by another driver.

Paranoid additional interpretation:

* Security-boundary bypass with sensitive resource access: +2 instead of only +1 cross-boundary concern. If BAR resources are freed and reused by another driver while a stale DMABUF mapping still allows access, this becomes a meaningful VFIO/device isolation bypass.
* Availability impact realistic: +1. Incorrect MMIO access after teardown or reuse can plausibly cause device malfunction or host-impacting device errors.

## 3. Reachability analysis

The bug is local, not network reachable. It requires VFIO PCI usage with DMABUF export support for MMIO regions. The attacker normally needs access to an assigned VFIO device or a process that can hold exported DMABUFs, so this is not full host-root by itself and should not be reduced to PR:H automatically.

Namespaces and containers may matter if VFIO device access is delegated to a VM manager, container, sandboxed service, or reduced-capability root process. In typical deployments, initial device assignment is administrative, but the vulnerable close/teardown window may be reachable by the less-privileged consumer that already owns the VFIO device fd or DMABUF.

Realistic exploitation depends on precise teardown timing and whether BAR resources are quickly reused by another driver. This makes exploitation less straightforward, but the resource lifetime and isolation implications are strong enough for manual review.

## 4. Severity interpretation

This is not ordinary generic kernel memory corruption. It is a stale device MMIO resource lifetime bug in a privileged VFIO PCI path. The realistic impact is at least Actionable Moderate because stale DMABUF access after function disable can violate expected revocation of MMIO access.

The paranoid interpretation reaches Strong Important candidate because the commit explicitly states that BAR resources may be freed and become available to another driver while DMABUF access may still exist. That creates a plausible confidentiality and integrity boundary issue across device ownership, even without a demonstrated arbitrary write or kernel-code-execution primitive.

## 5. One-sentence report phrase

VFIO PCI could leave a stale DMABUF mapping to MMIO BAR resources during device shutdown, allowing local VFIO users to retain unintended access after function disable and possible BAR reuse by another driver.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a local VFIO/device resource lifetime and isolation issue with plausible stale MMIO access across ownership changes. The tiny race window reduces reliability, but the potential boundary bypass and C/I impact make auto-closure unsafe.

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

Patch: vfio/pci: Clean up DMABUFs before disabling function [ Upstream
Commit: 4f1000a30f67cf7d328059242776a858611d5ef9
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4f1000a30f67cf7d328059242776a858611d5ef9

Changed files:
  drivers/vfio/pci/vfio_pci_core.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=4f1000a30f67cf7d328059242776a858611d5ef9

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

The original Linux kernel CVE announcement for CVE-2026-53322 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53322

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:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7

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: 5
  Paranoid ActionableScore: 7

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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).