[CVE-2026-98714][MODERATE 7.0] KVM: SVM: Update control fields on #VMEXIT if and only if VMRUN succeeded

[CVE-2026-98714][MODERATE 7.0] KVM: SVM: Update control fields on #VMEXIT if and only if VMRUN succeeded

[AL-KERNEL]

CVE: CVE-2026-98714
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: KVM: SVM: Update control fields on #VMEXIT if and only if VMRUN succeeded
Commit: 8676b29d186fcb5c1251d8152fc91d19421e5600
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8676b29d186fcb5c1251d8152fc91d19421e5600
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98714
Analysis date: Sat, 24 Oct 2026 10:36:34 -0400
ActionableScore: 4
ActionableScore lower bound: unknown
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
Failed VMRUN handling incorrectly retires pending VMCB control actions, allowing later host KVM execution to consume stale clean and ERAP state.

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

The original Linux kernel CVE announcement for CVE-2026-98714 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98714

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-2026-98714	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-98714 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC)	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:N/A:H';CWE-670;CWE-693;CWE-440;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.3';DESCR 'A KVM SVM control state logic error updates software VMCB state after a failed VMRUN even though AMD does not guarantee that the requested control actions were performed. Clearing ERAP_CONTROL_CLEAR_RAP and marking the VMCB clean can cause a later entry to omit an intended Return Address Predictor clear or to reuse control fields under an invalid cache assumption. For the CVSS the PR:L value reflects that reliable triggering requires control of a local KVM guest, nested SVM state, or a userspace VMM path rather than unauthenticated network access. No UAF, OOB access, arbitrary write, or proven host privilege escalation primitive is shown. The base impact is possible guest execution disruption. The paranoid case includes limited confidentiality risk from a missed ERAP isolation action and high availability impact from unresolved stale control behavior. Automated impact decision path. The original SimpleNet classifier selected MODERATE. The primary LLM estimated paranoid CVSS 5.3 and the production ActionableScore returned 4 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation 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 V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 0.0 and ActionableScore 0 with primitive class NONE and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4)	MAYBE	VIRT INIT SIMPLEFIX HARDWARE  KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED	-	-	checked

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

ActionableScore=4
PrimitiveClass=CLASS_B
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 4.
* Conservative score: 4; no floor or cap applied.
* Raw paranoid score: 4.
* Paranoid score: 4; confidentiality, host panic, or guest escape is not sufficiently shown for another point.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

* +1 weak/indirect active-state corruption: after failed VMRUN, vulnerable code clears `ERAP_CONTROL_CLEAR_RAP` and marks the VMCB clean despite hardware completion being architecturally unknown.
* +1 security-relevant stale-control leverage: a later VMRUN can consume the modified clean/control state and omit an intended RAP clear or control-field update.
* +1 downstream privileged consumer and credible guest/host boundary risk: host KVM consumes active VMCB state influenced by guest, nested-SVM, or VMM activity; the exact boundary reachability remains unresolved.
* +1 availability plausible: inconsistent VMCB state can disrupt subsequent guest execution, although host panic is not established.
* No UAF, OOB write, arbitrary write, controlled reclaim, disclosure, LPE, or proven host escape is shown.
* No confidentiality point: a missed ERAP clear suggests isolation concern but no concrete disclosure path.
* B4 is inapplicable: no mandatory authorization guard changes DENY to ALLOW.

3. Reachability analysis

The supplied summary grounds influence from a local KVM guest, nested-SVM state, or a userspace VMM, but does not prove which single principal can induce the failed VMRUN and all required follow-up entries. Guest-only versus compound guest/VMM triggering is therefore unresolved. Host-administrator powers, host UID 0, namespace capabilities, prior privileged VM setup, and timing reliability are not established. No network reachability is shown.

4. Primitive and severity reading

This is a non-UAF CLASS_B active structured-state consistency primitive. The write is in-bounds modification of live VMCB control metadata, not kernel-memory corruption. The later privileged consumer is a subsequent host VMRUN path. Shown effects are stale clean-state reuse and possible omission of an ERAP clear; host crash, information disclosure, and guest-to-host compromise remain speculative.

ImportantCandidate is YES under the active-state/trust-boundary rule because attacker-influenced live control state is later consumed by host KVM across a credible but incompletely resolved guest/VMM boundary. Auto-downgrade is disallowed pending boundary and downstream-consumer review.

5. One-sentence report phrase

Failed VMRUN handling incorrectly retires pending VMCB control actions, allowing later host KVM execution to consume stale clean and ERAP state.

6. Manual review advice

MANUAL CHECK REQUIRED

Confirm whether a malicious guest alone can force the failed-VMRUN/re-entry sequence and whether omitted ERAP or other dirty controls affect host isolation rather than only guest execution.

7. Call-site confidence

Call-site confidence: medium

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

Patch: KVM: SVM: Update control fields on #VMEXIT if and only if VMRUN succeeded
Commit: 8676b29d186fcb5c1251d8152fc91d19421e5600
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8676b29d186fcb5c1251d8152fc91d19421e5600

Commit description:

Leave control.erap_ctl and control.clean as-is in the VMCS if VMRUN fails,
because as per AMD:

  there's no explicit architectural guarantee about the behavior in the
  presence of VMRUN failures. So the best thing to do would be to assume
  that if VMRUN fails, the actions requested in the control fields may not
  have been performed.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260904170642.3291466-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  arch/x86/kvm/svm/svm.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=8676b29d186fcb5c1251d8152fc91d19421e5600

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

The original Linux kernel CVE announcement for CVE-2026-98714 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98714

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:N/A:H
  The Best / paranoid CVSS score: 5.3

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: 4

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).