CVE-2021-47567

Hard lockup via virtual emergency context address

Published May 24, 2024 · Updated May 23, 2026

Denial of service in the 32-bit PowerPC Linux kernel allows local users to cause a hard lockup through a vmap stack overflow. The overflow path in arch/powerpc/kernel/head_32.h addresses emergency_ctx virtually after the data MMU is disabled, preventing exception recovery. Reachability requires local low-privileged access and a 32-bit PowerPC kernel with virtual-mapped stacks; the bounded consequence is a host hang without disclosed data access or modification.

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

Denial of service in the 32-bit PowerPC Linux kernel allows local users to cause a hard lockup through a vmap stack overflow. The overflow path in arch/powerpc/kernel/head_32.h addresses emergency_ctx virtually after the data MMU is disabled, preventing exception recovery. Reachability requires local low-privileged access and a 32-bit PowerPC kernel with virtual-mapped stacks; the bounded consequence is a host hang without disclosed data access or modification.

The record

CVE
CVE-2021-47567
Published
May 24, 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 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

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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=3b234b4a6651ed6bdca94553aa0038fc7ded9271
  2. Affected versionversion=5.10
  3. Affected versionversion=5.9.5 <5.10
  4. Affected versionversion=c118c7303ad528be8ff2aea8cd1ee15452c763f0 <5bb60ea611db1e04814426ed4bd1c95d1487678e
  5. Affected versionversion=c118c7303ad528be8ff2aea8cd1ee15452c763f0 <c4e3ff8b8b1d54f0c755670174c453b06e17114b
  6. Affected versionversion=c118c7303ad528be8ff2aea8cd1ee15452c763f0 <dfe906da9a1abebdebe8b15bb3e66a2578f6c4c7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3b234b4a6651ed6bdca94553aa0038fc7ded9271; version=5.10; version=5.9.5 <5.10; version=c118c7303ad528be8ff2aea8cd1ee15452c763f0 <5bb60ea611db1e04814426ed4bd1c95d1487678e; version=c118c7303ad528be8ff2aea8cd1ee15452c763f0 <c4e3ff8b8b1d54f0c755670174c453b06e17114b; version=c118c7303ad528be8ff2aea8cd1ee15452c763f0 <dfe906da9a1abebdebe8b15bb3e66a2578f6c4c7

Published CVSS scores

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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