CVE-2021-47553

Kernel degradation via stale CPU idle-task state

Published May 24, 2024 · Updated May 23, 2026

Improper idle-task state reset in Linux 5.10.50 through 5.10.82 and other affected releases allows local users to degrade kernel execution. bringup_cpu() reuses an idle task without clearing stale KASAN shadow or resetting its saved SCS stack pointer before a CPU returns online. Reachability requires CPU hotplug access; repeated cycles produce false KASAN reports and progressively exhaust the idle task's shadow call stack.

CVSS severity7.8
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper idle-task state reset in Linux 5.10.50 through 5.10.82 and other affected releases allows local users to degrade kernel execution. bringup_cpu() reuses an idle task without clearing stale KASAN shadow or resetting its saved SCS stack pointer before a CPU returns online. Reachability requires CPU hotplug access; repeated cycles produce false KASAN reports and progressively exhaust the idle task's shadow call stack.

The record

CVE
CVE-2021-47553
Published
May 24, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-908, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 24, 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

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=1cb358b3ac1bb43aa8c4283830a84216dda65d39
  2. Affected versionversion=24c79a7e54ccfa29fb8cbf7ed8d1e48ff1ec6e3d
  3. Affected versionversion=3c51d82d0b7862d7d246016c74b4390fb1fa1f11 <e6ee7abd6bfe559ad9989004b34c320fd638c526
  4. Affected versionversion=5.10.50 <5.10.83
  5. Affected versionversion=5.12.17 <5.13
  6. Affected versionversion=5.13.2 <5.14
  7. Affected versionversion=5.14
  8. Affected versionversion=f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 <229c555260cb9c1ccdab861e16f0410f1718f302
  9. Affected versionversion=f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 <dce1ca0525bfdc8a69a9343bc714fbc19a2f04b3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1cb358b3ac1bb43aa8c4283830a84216dda65d39; version=24c79a7e54ccfa29fb8cbf7ed8d1e48ff1ec6e3d; version=3c51d82d0b7862d7d246016c74b4390fb1fa1f11 <e6ee7abd6bfe559ad9989004b34c320fd638c526; version=5.10.50 <5.10.83; version=5.12.17 <5.13; version=5.13.2 <5.14; version=5.14; version=f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 <229c555260cb9c1ccdab861e16f0410f1718f302; version=f1a0a376ca0c4ef1fc3d24e3e502acbb5b795674 <dce1ca0525bfdc8a69a9343bc714fbc19a2f04b3

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-908Use of Uninitialized Resource
T1499.004Application or System Exploitation

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo