CVE-2021-47454

Kernel scheduling fault via stale preemption decrement

Published May 22, 2024 · Updated May 23, 2026

Improper preemption handling in Linux allows local users to trigger a scheduling fault through PowerPC CPU hotplug. arch_cpu_idle_dead() wrongly calls preempt_enable() while offlining a CPU, decrementing an idle-task preemption count that must remain disabled. The flaw requires PREEMPT_COUNT and an offline-then-online CPU cycle; the resulting scheduling-while-atomic state disrupts kernel scheduling.

CVSS severity5.5
Medium
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

Improper preemption handling in Linux allows local users to trigger a scheduling fault through PowerPC CPU hotplug. arch_cpu_idle_dead() wrongly calls preempt_enable() while offlining a CPU, decrementing an idle-task preemption count that must remain disabled. The flaw requires PREEMPT_COUNT and an offline-then-online CPU cycle; the resulting scheduling-while-atomic state disrupts kernel scheduling.

The record

CVE
CVE-2021-47454
Published
May 22, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 22, 2024CVE publishedPublication date reported by the CVE source.
  2. May 23, 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=20a015e948b825afb47855de2efce7cae7c2608f
  2. Affected versionversion=2b6148ef2bd6d8ddc76e7873114f7769b6aa25f0
  3. Affected versionversion=2c669ef6979c370f98d4b876e54f19613c81e075 <3ea0b497a7a2fff6a4b7090310c9f52c91975934
  4. Affected versionversion=2c669ef6979c370f98d4b876e54f19613c81e075 <787252a10d9422f3058df9a4821f389e5326c440
  5. Affected versionversion=5.10.50 <5.10.76
  6. Affected versionversion=5.12.17 <5.13
  7. Affected versionversion=5.13.2 <5.14
  8. Affected versionversion=5.14
  9. Affected versionversion=bdf4d33e8342b90386156204e1da0cdfdb4bf146 <53770a411559cf7bc0906d1df319cc533d2f4f58

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=20a015e948b825afb47855de2efce7cae7c2608f; version=2b6148ef2bd6d8ddc76e7873114f7769b6aa25f0; version=2c669ef6979c370f98d4b876e54f19613c81e075 <3ea0b497a7a2fff6a4b7090310c9f52c91975934; version=2c669ef6979c370f98d4b876e54f19613c81e075 <787252a10d9422f3058df9a4821f389e5326c440; version=5.10.50 <5.10.76; version=5.12.17 <5.13; version=5.13.2 <5.14; version=5.14; version=bdf4d33e8342b90386156204e1da0cdfdb4bf146 <53770a411559cf7bc0906d1df319cc533d2f4f58

Published CVSS scores

5.5Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/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.

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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

T1499Endpoint Denial of Service

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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