[CVE-2026-64310][MODERATE REGULAR] crypto: ccp - Do not initialize SNP for SEV ioctls

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

CVE: CVE-2026-64310
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: crypto: ccp - Do not initialize SNP for SEV ioctls
Commit: 5181e88da99c3d1d41e25db3472a62b8d4b42cdd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5181e88da99c3d1d41e25db3472a62b8d4b42cdd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64310
Analysis date: Sat, 25 Jul 2026 07:37:32 -0400
ActionableScore: 4
ActionableScore lower bound: 2
Actionable bucket: Borderline. Manual review recommended, not Strong Important on current evidence
Manual review required: YES

Summary:
SEV-only ioctls could unnecessarily enter SNP initialization and clear global HSAVE_PA state after a firmware error, allowing a local process with `/dev/sev` access to crash an AMD SEV KVM host when a later VMRUN occurs.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-64310 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64310

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 REGULAR
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-2026-64310	MODERATE	CHECK WITH IMPACT FROM ORIG NN 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-665;CWE-703;CWE-404;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'SEV-only platform ioctls could enter a path that unnecessarily initializes SNP state while only SEV firmware is required. If SEV initialization fails while normal KVM VMs are active, the global MSR_VM_HSAVE_PA value may be cleared and a later VMRUN can fault in the host, causing a host crash. For the CVSS the PR:L is used for the paranoid score because a local process with delegated access to /dev/sev or a virtualization management account may be able to issue the affected SEV ioctls without full host administrator privileges. The issue is not network reachable and requires local access to the SEV device interface on an AMD SEV capable host. Impact is denial of service via host crash. No direct confidentiality or integrity impact is assigned because the patch context supports global virtualization state corruption leading to crash, not a concrete information leak or arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline. Manual review recommended, not Strong Important on current evidence (with actual score 3)	YES	INIT  INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=4
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: **2**
* Paranoid score: **4**
* Final recommended bucket: **Borderline. Manual review recommended, not Strong Important on current evidence**::

## 2. Signal breakdown

Conservative signals:

* **Firmware-mediated external influence: +1**
  The failure condition depends on SEV firmware initialization behavior and SEV/SNP platform state.
* **Reliable kernel crash / strong DoS: +1**
  If HSAVE_PA is cleared while normal KVM VMs are active, the next VMRUN may fault in the host and crash it.
* **Availability impact realistic: +1**
  The described impact is host-wide crash affecting running VMs, not only failure of the ioctl caller.
* **Privileged virtualization/device state corruption: +1**
  The bug affects global SEV/SNP or HSAVE_PA state used by KVM execution.
* **Common virtualization host relevance: +1**
  KVM plus AMD SEV is a meaningful deployment class, especially in virtualization platforms.
* **Requires admin/root or privileged device access in typical deployments: -2**
  Access to `/dev/sev` is usually restricted to root or a virtualization management service.
* **Hard preconditions / special state required: -1**
  Requires AMD SEV/SNP capable hardware, SEV init failure, active KVM VMs, and a later VMRUN.

Paranoid adjustment:

* Do not apply the full privilege penalty when `/dev/sev` access is delegated to a reduced-privilege virtualization service account or management context. This raises the practical concern from ordinary privileged DoS toward a manual-review case, but still does not show LPE or memory corruption.

No added signals:

* No generic memory corruption: **0**
* No UAF, OOB write, double free, or arbitrary write: **0**
* No confidentiality impact: **0**
* No integrity impact: **0**
* No remote/network reachability: **0**
* No privilege escalation primitive: **0**

## 3. Reachability analysis

The trigger is local through SEV platform ioctls such as `SEV_PDH_GEN`, `SEV_PEK_GEN`, `SEV_PEK_CSR`, `SEV_PEK_CERT_IMPORT`, and `SEV_PDH_CERT_EXPORT` on `/dev/sev`. In typical deployments this device is restricted to root or a virtualization management component, so conservative scoring treats it as privileged. In a cloud or hosting environment, however, access may be delegated to a service account or reduced-capability management process, so the paranoid score avoids treating this as equivalent to full host root.

The issue is not network reachable by packet input. It is hardware and configuration dependent: AMD SEV/SNP support must exist, SEV initialization must fail in the relevant way, and normal KVM VMs must be active so that a later VMRUN can hit the corrupted global state.

Call-site confidence: **medium**. The patch and commit message identify the ioctl path and the affected initialization helper, but the full caller tree and device permission model are not shown in the provided input.

## 4. Severity interpretation

This behaves like a **host DoS through privileged or semi-privileged virtualization state management**, not like a generic memory corruption vulnerability. The realistic impact is a kernel or host crash when active KVM VMs later execute VMRUN after HSAVE_PA has been cleared. Theoretical escalation beyond DoS is not supported by the patch context because there is no shown UAF, stale callback, arbitrary write, type confusion, controlled overwrite, or information disclosure path.

Conservative handling is ordinary Moderate or Low-like due to privileged access and hard preconditions. Paranoid handling is **borderline manual review** because the affected state is global KVM/SEV host state and delegated `/dev/sev` access may exist in real virtualization deployments.

## 5. One-sentence report phrase

SEV-only ioctls could unnecessarily enter SNP initialization and clear global HSAVE_PA state after a firmware error, allowing a local process with `/dev/sev` access to crash an AMD SEV KVM host when a later VMRUN occurs.

## 6. Manual review recommendation

**MANUAL CHECK RECOMMENDED**

Manual review is recommended because the issue affects global KVM/SEV host execution state and the practical severity depends heavily on `/dev/sev` permissions and virtualization management delegation. It is not an Important-class memory corruption candidate on current evidence, but it should not be blindly auto-closed without checking product-specific SEV exposure.

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UPSTREAM PATCH SUMMARY
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Patch: crypto: ccp - Do not initialize SNP for SEV ioctls
Commit: 5181e88da99c3d1d41e25db3472a62b8d4b42cdd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5181e88da99c3d1d41e25db3472a62b8d4b42cdd

Commit description:

Sashiko notes:

> if SEV initialization fails and KVM is actively running normal VMs, could a
> userspace process trigger this code path via /dev/sev ioctls (e.g.,
> SEV_PDH_GEN) and zero out MSR_VM_HSAVE_PA globally? Would the next VMRUN
> execution for an active VM trigger a general protection fault and crash the
> host?

sev_move_to_init_state() is called for ioctls requiring only SEV firmware:
SEV_PEK_GEN, SEV_PDH_GEN, SEV_PEK_CSR, SEV_PEK_CERT_IMPORT, and
SEV_PDH_CERT_EXPORT. After the firmware command, it does SEV_SHUTDOWN on
the SEV firmware. Since these commands do not require SNP to be
initialized, skip it by calling __sev_platform_init_locked() which only
initializes the SEV firmware. This way SNP is not Initialized at all, and
HSAVE_PA is not cleared.

The previous code saved any SEV initialization firmware error to
init_args.error and then threw it away and hardcoded the return value of
INVALID_PLATFORM_STATE regardless of the real firmware error. This patch
changes it to surface the underlying error, which is hopefully both more
useful and doesn't cause any problems.

Note that it is still safe to call __sev_firmware_shutdown() directly: it
calls __sev_snp_shutdown_locked(), which skips SNP shutdown if SNP was not
initialized.

Fixes: ceac7fb ("crypto: ccp - Ensure implicit SEV/SNP init and shutdown in ioctls")
Reported-by: Sashiko
Assisted-by: Gemini:gemini-3.1-pro-preview
Link: https://sashiko.dev/#/patchset/20260324161301.1353976-1-tycho%40kernel.org
CC: <stable@vger.kernel.org>
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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=5181e88da99c3d1d41e25db3472a62b8d4b42cdd

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

The original Linux kernel CVE announcement for CVE-2026-64310 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64310

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: 2
  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: NO
Published priority for this report (same as in Subject): MODERATE REGULAR

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).