CVE-2021-47226

Cross-task register corruption via failed XRSTOR

Published May 21, 2024 · Updated Aug 5, 2026

FPU state corruption in Linux allows local users to alter another task's registers through a failed XRSTOR during signal restoration. The __fpu__restore_sig() path can leave partially modified hardware registers attributed to a victim after XRSTOR faults, then let that task resume without restoring its saved FPU state. Exploitation requires unprivileged local execution on x86 and a sibling-thread unmap race; the bounded result is victim register corruption that can fault or abort the process.

CVSS severity7.1
High
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

FPU state corruption in Linux allows local users to alter another task's registers through a failed XRSTOR during signal restoration. The __fpu__restore_sig() path can leave partially modified hardware registers attributed to a victim after XRSTOR faults, then let that task resume without restoring its saved FPU state. Exploitation requires unprivileged local execution on x86 and a sibling-thread unmap race; the bounded result is victim register corruption that can fault or abort the process.

The record

CVE
CVE-2021-47226
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-203, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=1d731e731c4cd7cbd3b1aa295f0932e7610da82f <002665dcba4bbec8c82f0aeb4bd3f44334ed2c14
  2. Affected versionversion=1d731e731c4cd7cbd3b1aa295f0932e7610da82f <a7748e021b9fb7739e3cb88449296539de0b6817
  3. Affected versionversion=1d731e731c4cd7cbd3b1aa295f0932e7610da82f <d8778e393afa421f1f117471144f8ce6deb6953a
  4. Affected versionversion=5.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1d731e731c4cd7cbd3b1aa295f0932e7610da82f <002665dcba4bbec8c82f0aeb4bd3f44334ed2c14; version=1d731e731c4cd7cbd3b1aa295f0932e7610da82f <a7748e021b9fb7739e3cb88449296539de0b6817; version=1d731e731c4cd7cbd3b1aa295f0932e7610da82f <d8778e393afa421f1f117471144f8ce6deb6953a; version=5.2

Published CVSS scores

7.1NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-203Observable Discrepancy
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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