[CVE-2026-72288][MODERATE 7.0] KVM: arm64: vgic: Handle race between interrupt affinity change and LPI disabling

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

CVE: CVE-2026-72288
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: KVM: arm64: vgic: Handle race between interrupt affinity change and LPI disabling
Commit: d19dca8194ebed371e624331c6be2cb73b562caf
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d19dca8194ebed371e624331c6be2cb73b562caf
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72288
Analysis date: Sat, 15 Aug 2026 07:49:38 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in arm64 KVM VGIC LPI handling can leave `vgic_prune_ap_list()` operating on a freed IRQ object after locks are dropped and reacquired, creating a host kernel UAF that is most likely a DoS but requires manual review for possible guest-to-host impact.

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

The original Linux kernel CVE announcement for CVE-2026-72288 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72288

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-2026-72288	MODERATE	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:C/C:H/I:H/A:H';CWE-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A race in KVM arm64 VGIC LPI handling can occur when one vCPU disables LPIs for another vCPU while a different vCPU concurrently migrates a pending LPI. vgic_prune_ap_list can drop the IRQ and AP list locks and later continue operating on an IRQ object that may have been freed in the meantime, creating a use after free in the host kernel KVM path. For the CVSS the PR:L is used because practical triggering requires the ability to run or control a guest or otherwise access the KVM execution context, but it does not require full host administrator privileges. The issue is not directly network reachable and is triggered through guest or local virtualization control paths rather than packet traffic. Impact is at least denial of service via host kernel crash and in the worst case may allow confidentiality or integrity impact due to memory corruption across the guest to host boundary.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	VIRT RACE UAF DMAorINTERRUPT HARDWARE LINUS KPANIC  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN6	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local low privilege or guest trigger: +1. Triggering requires control of a KVM guest or access to the KVM execution context, not full host root.
* Memory corruption, weak primitive: +1. The patch explicitly describes a UAF, but it is race dependent and does not show attacker controlled reclaim, type confusion, callback control, or arbitrary write.
* Real lifetime corruption: +1. The fix takes an IRQ reference before dropping locks, which directly addresses object lifetime across unlock and relock.
* Reliable kernel crash / strong DoS: +1. A host kernel UAF in KVM VGIC code can realistically crash the host.
* Broad or important subsystem exposure: +1. KVM is a common virtualization subsystem, although the exact VGIC LPI path is configuration dependent.
* Hard or unreliable race / special timing required: -1. The commit requires a race between LPI disabling and interrupt migration.

Paranoid additional signal:

* Privileged hypervisor memory corruption path: +1. The UAF is in host KVM interrupt controller state and crosses a guest to host security boundary, but the race UAF downgrade rule keeps this at weak/manual review relevance rather than strong LPE.

No remote/network signal is awarded. No firmware-mediated signal is awarded.

## 3. Reachability analysis

The likely attacker is a local user with access to `/dev/kvm`, a VM tenant, or a process able to run and influence an arm64 KVM guest using VGIC LPIs. In many deployments this is not full host root, but it is also not reachable by an arbitrary remote network attacker. Namespace or container exposure matters if `/dev/kvm` is delegated into a container or to a reduced privilege virtualization service. The affected path is not packet-triggered and depends on arm64 KVM VGIC LPI behavior, multiple vCPUs, interrupt affinity movement, and LPI disabling. The race condition makes reliable exploitation harder, but the bug is in a host hypervisor path and therefore should not be auto-closed.

Call-site confidence: high. The supplied patch shows the lifetime fix directly in `vgic_prune_ap_list()` and the LPI cleanup behavior in `vgic_flush_pending_lpis()`.

## 4. Severity interpretation

This is more than an ordinary Moderate because the patch explicitly fixes a UAF in KVM host-side VGIC code. Realistic demonstrated impact is most clearly host DoS via kernel crash. Theoretical privilege escalation or guest-to-host impact is plausible enough for manual review because it is a host kernel UAF reachable from guest-controlled virtualization activity, but the patch does not demonstrate controlled reclaim, write-after-free, callback dispatch, or an arbitrary write primitive. Therefore the conservative score remains Borderline Manual Review, while the paranoid score reaches Actionable Moderate.

## 5. One-sentence report phrase

A race in arm64 KVM VGIC LPI handling can leave `vgic_prune_ap_list()` operating on a freed IRQ object after locks are dropped and reacquired, creating a host kernel UAF that is most likely a DoS but requires manual review for possible guest-to-host impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. YES REQUIRES MANUAL CHECK.

Reason: explicit UAF in KVM host hypervisor code, guest-influenced race conditions, and possible guest-to-host security boundary relevance, even though a practical LPE primitive is not demonstrated.

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

Patch: KVM: arm64: vgic: Handle race between interrupt affinity change and LPI disabling
Commit: d19dca8194ebed371e624331c6be2cb73b562caf
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=d19dca8194ebed371e624331c6be2cb73b562caf

Commit description:

Hyunwoo Kim reports some really bad races should the following
situation occur:

- LPI-I is pending in vcpu-B's AP list
- vcpu-A writes to vcpu-B's RD to disable its LPIs
- vcpu-C moves I from B to C

If the last two race nicely enough, vgic_prune_ap_list() can drop
the irq and AP list locks, reacquire them, and in the interval
the irq has been freed. UAF follows.

The fix is two-fold:

- Before dropping the irq and ap_list locks, take a reference on
  the irq

- Do not try to handle migration of the pending bit: there is no
  expectation that this state is retained, as per the architecture

With that, we're sure that the interrupt is still around, and we
safely remove it from the AP list as it has no target at this
stage (unless another interrupt fires, but that's another story).

Reported-by: Hyunwoo Kim <imv4bel@gmail.com>
Tested-by: Hyunwoo Kim <imv4bel@gmail.com>
Link: https://lore.kernel.org/r/ailsCnyoS82r_QRz@v4bel
Link: https://patch.msgid.link/20260615181625.3029352-1-maz@kernel.org
Fixes: 5dd4b92 ("KVM: arm/arm64: vgic: Add refcounting for IRQs")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  arch/arm64/kvm/vgic/vgic.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=d19dca8194ebed371e624331c6be2cb73b562caf

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

The original Linux kernel CVE announcement for CVE-2026-72288 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72288

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:C/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:C/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).