CVE-2021-47566

Kernel crash via improper user-buffer clearing

Published May 24, 2024 · Updated May 11, 2026

Improper user-buffer clearing in Linux kernel 3.0 and later allows local users with vmcore access to trigger a kernel crash. The read_from_oldmem path uses memset() on a user-space destination when a vmcore callback reports zero-filled offline memory, bypassing clear_user() and its SMAP handling. Triggering the fault requires permission to read /proc/vmcore, an x86-64 CPU with SMAP, and a virtio-mem device with logically unplugged memory in an added block.

CVSS severityUnavailable
Unscored
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper user-buffer clearing in Linux kernel 3.0 and later allows local users with vmcore access to trigger a kernel crash. The read_from_oldmem path uses memset() on a user-space destination when a vmcore callback reports zero-filled offline memory, bypassing clear_user() and its SMAP handling. Triggering the fault requires permission to read /proc/vmcore, an x86-64 CPU with SMAP, and a virtio-mem device with logically unplugged memory in an added block.

The record

CVE
CVE-2021-47566
Published
May 24, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. May 24, 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

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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=3.0
  2. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <33a7d698f30fa0b99d50569e9909d3baa65d8f6a
  3. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1
  4. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <99d348b82bcb36171f24411d3f1a15706a2a937a
  5. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <9ef384ed300d1bcfb23d0ab0b487d544444d4b52
  6. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <a8a917058faf4abaec9fb614bb6d5f8fe3529ec6
  7. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <a9e164bd160be8cbee1df70acb379129e3cd2e7c
  8. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <c1e63117711977cc4295b2ce73de29dd17066c82
  9. Affected versionversion=997c136f518c5debd63847e78e2a8694f56dcf90 <fd7974c547abfb03072a4ee706d3a6f182266f89

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=3.0; version=997c136f518c5debd63847e78e2a8694f56dcf90 <33a7d698f30fa0b99d50569e9909d3baa65d8f6a; version=997c136f518c5debd63847e78e2a8694f56dcf90 <7b3a34f08d11e7f05cd00b8e09adaa15192f0ad1; version=997c136f518c5debd63847e78e2a8694f56dcf90 <99d348b82bcb36171f24411d3f1a15706a2a937a; version=997c136f518c5debd63847e78e2a8694f56dcf90 <9ef384ed300d1bcfb23d0ab0b487d544444d4b52; version=997c136f518c5debd63847e78e2a8694f56dcf90 <a8a917058faf4abaec9fb614bb6d5f8fe3529ec6; version=997c136f518c5debd63847e78e2a8694f56dcf90 <a9e164bd160be8cbee1df70acb379129e3cd2e7c; version=997c136f518c5debd63847e78e2a8694f56dcf90 <c1e63117711977cc4295b2ce73de29dd17066c82; version=997c136f518c5debd63847e78e2a8694f56dcf90 <fd7974c547abfb03072a4ee706d3a6f182266f89

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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

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Your stack

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