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CVE-2021-38198: arch/x86/kvm/mmu/paging_tmpl.h in the Linux kernel before 5.12.11 incorrectly computes the access permissio...

arch/x86/kvm/mmu/paging_tmpl.h in the Linux kernel before 5.12.11 incorrectly computes the access permissions of a shadow page, leading to a missing guest protection page fault.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This CVE affects the Linux kernel’s x86 KVM virtualization memory handling before 5.12.11. The kernel could miscalculate shadow page permissions and miss a guest protection fault. Business urgency depends on whether the organization runs KVM hosts, especially with less-trusted guest workloads.

Executive priority

Prioritize patch confirmation for KVM virtualization infrastructure. The severity is not scored in the supplied data, but virtualization isolation issues can carry high business impact when untrusted guests share hosts.

Technical view

The issue is in arch/x86/kvm/mmu/paging_tmpl.h. Incorrect shadow page access-permission computation may suppress an expected guest protection page fault. The provided sources identify Linux before 5.12.11 and Debian LTS kernel security updates, but do not provide CVSS, CWE, exploitability details, or full impact boundaries.

Likely exposure

Most relevant exposure is x86 Linux systems using KVM virtualization on kernels before 5.12.11 or older vendor kernels without backported fixes. Systems not running KVM guest workloads are less likely to be materially exposed based on the described vulnerable component.

Exploitation context

The bundle does not cite active exploitation, public exploit use, or KEV listing. Treat exploitation status as unconfirmed. The plausible security context is guest-to-hypervisor or guest-isolation weakness, but the sources do not fully define practical impact.

Researcher notes

Evidence is sparse: the CVE text names the vulnerable file and behavior, while the Linux commit and 5.12.11 changelog indicate correction. Debian advisories show downstream security handling. Do not assume broader product impact or active exploitation without additional vendor evidence.

Mitigation direction

  • Update affected Linux kernels to 5.12.11 or a vendor-patched equivalent.
  • Apply relevant Debian LTS kernel security updates where applicable.
  • Reboot hosts after kernel updates to load the fixed kernel.
  • Check distribution advisories for backported fixes on older maintained kernels.
  • Avoid less-trusted guest workloads on unpatched KVM hosts until remediated.

Validation and detection

  • Inventory Linux KVM hosts and record running kernel versions.
  • Confirm whether kernels are before 5.12.11 or vendor-backported patched builds.
  • Review package changelogs or advisories for CVE-2021-38198 coverage.
  • Verify hosts rebooted into the updated kernel after patching.
  • Prioritize validation on virtualization hosts running external or untrusted guests.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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