CVE-2021-47465

Kernel memory corruption via undersized emergency stack frame

Published May 22, 2024 · Updated Aug 5, 2026

Out-of-bounds writes in Linux KVM on PowerPC systems starting with 5.2 allow local users to corrupt adjacent kernel stack memory. idle_kvm_start_guest() writes its backchain, CR, and LR above the emergency-stack allocation, then saves nonvolatile registers into an undersized frame. Local users must reach the Book3S HV guest-start path; the corruption overlaps other emergency or IRQ stacks and can crash the host under extreme stack pressure.

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

Out-of-bounds writes in Linux KVM on PowerPC systems starting with 5.2 allow local users to corrupt adjacent kernel stack memory. idle_kvm_start_guest() writes its backchain, CR, and LR above the emergency-stack allocation, then saves nonvolatile registers into an undersized frame. Local users must reach the Book3S HV guest-start path; the corruption overlaps other emergency or IRQ stacks and can crash the host under extreme stack pressure.

The record

CVE
CVE-2021-47465
Published
May 22, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-674
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 22, 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=10d91611f426d4bafd2a83d966c36da811b2f7ad <6d077c37c4643394b1bae9682da48164fc147ea8
  2. Affected versionversion=10d91611f426d4bafd2a83d966c36da811b2f7ad <80bbb0bc3a0288442f7fe6fc514f4ee1cb06ccb7
  3. Affected versionversion=10d91611f426d4bafd2a83d966c36da811b2f7ad <9b4416c5095c20e110c82ae602c254099b83b72f
  4. Affected versionversion=10d91611f426d4bafd2a83d966c36da811b2f7ad <fbd724c49bead048ae9fc1a5b7bff2fb3e54f855
  5. Affected versionversion=5.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=10d91611f426d4bafd2a83d966c36da811b2f7ad <6d077c37c4643394b1bae9682da48164fc147ea8; version=10d91611f426d4bafd2a83d966c36da811b2f7ad <80bbb0bc3a0288442f7fe6fc514f4ee1cb06ccb7; version=10d91611f426d4bafd2a83d966c36da811b2f7ad <9b4416c5095c20e110c82ae602c254099b83b72f; version=10d91611f426d4bafd2a83d966c36da811b2f7ad <fbd724c49bead048ae9fc1a5b7bff2fb3e54f855; version=5.2

Published CVSS scores

7.1CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/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.

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-674Uncontrolled Recursion

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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