CVE-2021-47296

Host crash via unbalanced KVM vCPU load

Published May 21, 2024 · Updated Aug 5, 2026

Denial of service in PowerPC KVM in Linux 4.18 through 5.13.5 allows local users to crash the host via a crafted vCPU ioctl. kvm_arch_vcpu_ioctl calls vcpu_load before copying user data and returns on copy failure without calling vcpu_put, corrupting preemption-notifier state. Access to /dev/kvm on a PowerPC host is required, and an invalid userspace pointer can cause a kernel hang, oops, or panic.

CVSS severity5.5
Medium
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

Denial of service in PowerPC KVM in Linux 4.18 through 5.13.5 allows local users to crash the host via a crafted vCPU ioctl. kvm_arch_vcpu_ioctl calls vcpu_load before copying user data and returns on copy failure without calling vcpu_put, corrupting preemption-notifier state. Access to /dev/kvm on a PowerPC host is required, and an invalid userspace pointer can cause a kernel hang, oops, or panic.

The record

CVE
CVE-2021-47296
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499.004
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=4.18
  2. Affected versionversion=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <9bafc34dc4ad0cef18727c557f21ed3c3304df50
  3. Affected versionversion=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <a4a488915feaad38345cc01b80d52e8200ff5209
  4. Affected versionversion=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <bc4188a2f56e821ea057aca6bf444e138d06c252
  5. Affected versionversion=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <e14ef1095387f764d95614d3ec9e4d07c82a3533
  6. Affected versionversion=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <f38527f1890543cdfca8dfd06f75f9887cce6151

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.18; version=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <9bafc34dc4ad0cef18727c557f21ed3c3304df50; version=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <a4a488915feaad38345cc01b80d52e8200ff5209; version=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <bc4188a2f56e821ea057aca6bf444e138d06c252; version=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <e14ef1095387f764d95614d3ec9e4d07c82a3533; version=b3cebfe8c1cadf1817939dcc3688a2504a69c662 <f38527f1890543cdfca8dfd06f75f9887cce6151

Published CVSS scores

5.5CanonicalCVSS: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
4.7SUSECVSS:3.1/AV:L/AC:H/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

CWE-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation

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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