[CVE-2026-64307][MODERATE 7.0] crypto: ccp - Do not initialize SNP for ioctl(SNP_CONFIG) [ Upstream

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

CVE: CVE-2026-64307
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: crypto: ccp - Do not initialize SNP for ioctl(SNP_CONFIG) [ Upstream
Commit: 345a6e869b33687e9268044bcaeeefd7c61da675
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=345a6e869b33687e9268044bcaeeefd7c61da675
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64307
Analysis date: Sat, 25 Jul 2026 14:58:21 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A local SEV SNP_CONFIG ioctl path could retry SNP initialization when SNP was not initialized, potentially disrupting global SEV/KVM host state and causing a later VMRUN fault and host denial of service under specific virtualization conditions.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64307 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64307

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-64307	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:U/C:N/I:N/A:H';CWE-703;CWE-754;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A local SEV device ioctl path can retry SNP initialization through SNP_CONFIG when SNP is not already initialized. If SEV or SNP initialization previously failed while KVM is running normal VMs, this can disturb global SEV state such as MSR_VM_HSAVE_PA and make a later VMRUN fault in the host. For the CVSS the PR:L is used for the paranoid score because writable access to /dev/sev may be delegated to a virtualization service account, group, or reduced capability root in some deployments. The issue is not network reachable and requires local access to the SEV control device. Impact is denial of service of the host through a crash or fatal fault in the virtualization path. No direct confidentiality or integrity primitive is visible from the patch, so the impact is kept as C:N/I:N/A:H.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	DANGER INIT IMPROVEONLY  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Reliable kernel crash / strong DoS: +1. The commit describes a path where retrying SNP initialization can disturb global SEV state and make a later VMRUN fault in the host.
* Availability impact realistic: +1. The impact is host-level virtualization failure or crash, not just a local process failure.
* Practical exploit chain strongly implied: +1. The described chain is local /dev/sev ioctl -> SNP reinitialization attempt -> possible MSR_VM_HSAVE_PA disruption -> later VMRUN fault.
* Hard or unreliable race / special condition required: -1. The issue depends on SEV or SNP initialization failure and active KVM VMs.
* Requires admin/root/CAP-style access in typical deployments: -2. Writable /dev/sev access is normally restricted to privileged virtualization management.
* Rare/configuration-dependent subsystem: -1. Requires AMD SEV/SNP-capable systems and the affected initialization state.

Paranoid additional interpretation:

* Reduced-privilege virtualization service exposure: +1. In some deployments /dev/sev may be available to a virtualization service account, group, container root, or reduced-capability root, so PR:L is more realistic than full host root.
* Privileged device-management state corruption concern: +1. The affected state is global SEV/KVM host execution state, including HSAVE-related state, which is high-value even though no memory corruption primitive is shown.
* Do not add LPE or C/I impact. The patch supports host DoS, but not UAF, OOB write, arbitrary write, credential corruption, info leak, or guest-to-host code execution.

## 3. Reachability analysis

The bug is locally reachable through the SEV device ioctl path, specifically SNP_CONFIG behavior when SNP is not already initialized. In typical deployments this requires privileged access to /dev/sev, so the conservative view treats it as admin-controlled. The paranoid view uses PR:L-style reasoning because virtualization stacks may delegate SEV device access to a service account or reduced-privilege management process rather than full host root.

It is not network reachable by itself. A remote tenant or guest does not directly trigger the ioctl unless an additional management-plane path exposes it. The vulnerable condition is also configuration-dependent: AMD SEV/SNP support must exist, SNP initialization must be in the relevant failed or uninitialized state, and KVM VMs must be active for the described host crash path to matter.

## 4. Severity interpretation

This behaves more like an actionable Moderate than an ordinary Low/Moderate cleanup because the failure can affect host virtualization stability and active VMs. It is not an Important-class memory corruption issue based on the provided patch because there is no demonstrated UAF, stale callback, overwrite, object confusion, or attacker-controlled memory primitive.

The realistic impact is host DoS under special conditions. The paranoid score is elevated because the affected state is global SEV/KVM execution state and because reduced-privilege virtualization service access can make PR:L more appropriate than PR:H in real deployments.

## 5. One-sentence report phrase

A local SEV SNP_CONFIG ioctl path could retry SNP initialization when SNP was not initialized, potentially disrupting global SEV/KVM host state and causing a later VMRUN fault and host denial of service under specific virtualization conditions.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Manual review is required because the issue touches SEV/SNP initialization and KVM host execution state, and deployment-specific /dev/sev permissions can change the practical privilege requirement from full administrator to a reduced-privilege virtualization service context.

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UPSTREAM PATCH SUMMARY
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Patch: crypto: ccp - Do not initialize SNP for ioctl(SNP_CONFIG) [ Upstream
Commit: 345a6e869b33687e9268044bcaeeefd7c61da675
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=345a6e869b33687e9268044bcaeeefd7c61da675

Changed files:
  drivers/crypto/ccp/sev-dev.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=345a6e869b33687e9268044bcaeeefd7c61da675

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

The original Linux kernel CVE announcement for CVE-2026-64307 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64307

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:H/UI:N/S:U/C:N/I:N/A:H
  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: 3
  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: NO
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).