CVE-2021-47228

SEV guest boot crash via unencrypted EFI mapping

Published May 21, 2024 · Updated May 11, 2026

Improper memory mapping in the Linux kernel allows attackers to crash SEV guests during boot under specific EFI runtime conditions. The __ioremap_check_other() function fails to mark EFI boot-services data preserved with EFI_MEMORY_RUNTIME for encrypted mapping, so an SEV guest reads reserved memory with the wrong encryption state. The failure requires an x86 SEV guest and a driver that reserves EFI boot-services data for runtime use; the documented consequence is a boot-time general protection fault.

CVSS severity6.2
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper memory mapping in the Linux kernel allows attackers to crash SEV guests during boot under specific EFI runtime conditions. The __ioremap_check_other() function fails to mark EFI boot-services data preserved with EFI_MEMORY_RUNTIME for encrypted mapping, so an SEV guest reads reserved memory with the wrong encryption state. The failure requires an x86 SEV guest and a driver that reserves EFI boot-services data for runtime use; the documented consequence is a boot-time general protection fault.

The record

CVE
CVE-2021-47228
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.10
  2. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <208bb686e7fa7fff16e8fa78ff0db34aa9acdbd7
  3. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <8d651ee9c71bb12fc0c8eb2786b66cbe5aa3e43b
  4. Affected versionversion=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <b7a05aba39f733ec337c5b952e112dd2dc4fc404

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.10; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <208bb686e7fa7fff16e8fa78ff0db34aa9acdbd7; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <8d651ee9c71bb12fc0c8eb2786b66cbe5aa3e43b; version=58c909022a5a56cd1d9e89c8c5461fd1f6a27bb5 <b7a05aba39f733ec337c5b952e112dd2dc4fc404

Published CVSS scores

6.2CISA-ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.2Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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