[CVE-2026-98433][LOW] KVM: PPC: Book3S HV: fix secure device page leak on uv_page_in() failure [ Upstream

[CVE-2026-98433][LOW] KVM: PPC: Book3S HV: fix secure device page leak on uv_page_in() failure [ Upstream

[AL-KERNEL]

CVE: CVE-2026-98433
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: KVM: PPC: Book3S HV: fix secure device page leak on uv_page_in() failure [ Upstream
Commit: ed2f2ff63cb7e71204096e765c6d02c3b6974b95
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed2f2ff63cb7e71204096e765c6d02c3b6974b95
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98433
Analysis date: Mon, 19 Oct 2026 05:20:51 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A failed Ultravisor page-in operation can permanently leak a secure device page and leave its GFN unusable for the VM lifetime, with repeated failures potentially exhausting the finite secure-memory pool on affected POWER9 or POWER10 PEF hosts.

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

The original Linux kernel CVE announcement for CVE-2026-98433 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98433

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: LOW
Manual review required: NO

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
======================================================================

CVE-2026-98433	LOW	https://www.kernelcve.org/list/?q=CVE-2026-98433 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT LOW AEGIS_AS=0 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both LOW)	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'A persistent secure device page leak occurs in KVM PPC Book3S HV when kvmppc_uvmem_get_page succeeds but the following uv_page_in operation fails. The failed path retains the page reference and lock related state, leaks the private allocation, keeps the bitmap entry occupied, and leaves the affected GFN marked as secure for the remaining lifetime of the VM. Repeated failures may consume the firmware bounded secure memory pool and eventually prevent secure page migration or continued operation of protected guests. For the CVSS the PR:L value is used because triggering requires control of a local KVM process or a guest context on a POWER9 or POWER10 host configured with Ultravisor and PEF, but does not necessarily require unrestricted host administrator privileges. The issue is not network reachable. AC:H reflects the need for uv_page_in to fail after the secure page has already been allocated. The demonstrated impact is persistent resource retention and reduced availability. No UAF, OOB access, arbitrary write, information disclosure, or privilege escalation primitive is supported by this code path. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 4.7 and the production ActionableScore returned 0 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE to LOW because the CVSS score, vector or bug class threshold rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH. The independent weaker Aegis shadow evaluated CVSS 2.6 and ActionableScore 0 with primitive class CLASS_C and manual review RECOMMENDED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0)	MAYBE	VIRT LEAK HARDWARE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=0
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: -1
* Conservative score: 0
* Raw paranoid score: 0
* Paranoid score: 0
* The conservative result was normalized from -1 to the minimum score of 0. No security-primitive floor applies.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Conservative signals:

* +1 Concrete persistent kernel resource/reference leak. After `kvmppc_uvmem_get_page()` succeeds, an error from `uv_page_in()` leaves the device-page reference, bitmap entry, private allocation, page lock state, and secure GFN state unreleased.
* -2 Rare hardware-only path. The vulnerable implementation requires an IBM POWER9 or POWER10 host configured with Ultravisor and PEF secure-guest support.

Paranoid signals:

* +1 Concrete persistent kernel resource/reference leak.
* +1 Persistent finite-pool exhaustion concern. Every occurrence permanently consumes an entry from the firmware-bounded secure-memory pool and leaves one GFN unusable until the VM terminates. Repeated occurrences can therefore impair secure-page migration or protected-VM operation.
* -2 Rare hardware-only path.

Not awarded:

* No UAF or post-lifetime dereference is established. The object remains allocated because its reference is not dropped.
* No OOB access, arbitrary write, controlled reclaim, double release, authorization bypass, or privilege-escalation primitive is established.
* No reliable host crash or host-wide exhaustion is demonstrated.
* No local-unprivileged bonus is awarded because the evidence does not show that a guest or ordinary host user can deliberately and repeatedly force `uv_page_in()` failures.
* No KVM guest-to-host leverage is awarded. Guest involvement in secure page migration does not establish guest control over the complete failing sequence.
* B5-R does not apply because there is no heap OOB write.
* B3-PENDING does not apply because no shared-backing write is present.
* B4-PENDING does not apply because no authorization decision changes from DENY to ALLOW.

3. Reachability analysis

The affected path exists only on POWER9 or POWER10 systems using KVM Book3S HV with Ultravisor and PEF secure guests. The immediate prerequisite is successful allocation by `kvmppc_uvmem_get_page()` followed by failure of `uv_page_in()`, for example because of an Ultravisor resource failure or pool pressure.

The evidence does not resolve whether malicious guest code alone can force this exact sequence repeatedly. A local VMM with `/dev/kvm` access can manage the VM, but the supplied code does not establish that the VMM can reliably control the Ultravisor failure condition. Host-administrator participation is therefore not proven, but below-host-admin complete reachability is also not proven. The attacker model remains unresolved rather than guest-only.

No namespace-scoped trigger, network trigger, timing race, or remote interface is shown. Prior host setup of Ultravisor, PEF, and a secure VM is required.

4. Primitive and severity interpretation

The exact primitive is a missing reference and resource release on an error path. The page remains live rather than becoming dangling, so this is not a UAF, double release, or memory-corruption condition. It is a persistent resource leak accompanied by stale secure-GFN bookkeeping.

The demonstrated consequence is loss of one firmware-managed secure page and one usable GFN for the lifetime of the VM per occurrence. The defensible paranoid consequence is exhaustion of the finite secure-memory pool after repeated failures. Host-wide failure, cross-VM consumption, guest-to-host corruption, confidentiality loss, integrity compromise, and privilege escalation remain unsupported.

`PrimitiveClass=CLASS_C` reflects availability and invalid-state behavior without an independently useful corruption primitive. `ImportantCandidate=NO` because neither strong corruption nor an unresolved security-boundary primitive exists. `AutoDowngradeAllowed=YES` because the issue is a specialized resource leak with no demonstrated attacker-controlled accumulation or Important-grade consequence.

5. One-sentence report phrase

A failed Ultravisor page-in operation can permanently leak a secure device page and leave its GFN unusable for the VM lifetime, with repeated failures potentially exhausting the finite secure-memory pool on affected POWER9 or POWER10 PEF hosts.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

The patch establishes a specialized persistent resource leak but no UAF, OOB write, authorization bypass, network exposure, or credible privilege-escalation primitive.

7. Call-site confidence

Call-site confidence: medium

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

Patch: KVM: PPC: Book3S HV: fix secure device page leak on uv_page_in() failure [ Upstream
Commit: ed2f2ff63cb7e71204096e765c6d02c3b6974b95
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed2f2ff63cb7e71204096e765c6d02c3b6974b95

Changed files:
  arch/powerpc/kvm/book3s_hv_uvmem.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=ed2f2ff63cb7e71204096e765c6d02c3b6974b95

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

The original Linux kernel CVE announcement for CVE-2026-98433 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98433

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:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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: unknown
  Paranoid ActionableScore: 0

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).