CVE-2021-47639

Host privilege escalation via stale TDP MMU roots

Published Feb 26, 2025 · Updated Aug 5, 2026

Use-after-free in Linux KVM 5.13 allows local users with /dev/kvm access to disclose or modify kernel memory or crash the host. TDP MMU range unmapping omits invalid roots, allowing delayed SPTE zapping to reference freed page state after an mmu_notifier completes. Exploitation requires an account permitted to open /dev/kvm and control concurrent memslot updates and backing-memory unmapping; guest-only execution is insufficient.

CVSS severity7.8
High
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Linux KVM 5.13 allows local users with /dev/kvm access to disclose or modify kernel memory or crash the host. TDP MMU range unmapping omits invalid roots, allowing delayed SPTE zapping to reference freed page state after an mmu_notifier completes. Exploitation requires an account permitted to open /dev/kvm and control concurrent memslot updates and backing-memory unmapping; guest-only execution is insufficient.

The record

CVE
CVE-2021-47639
Published
Feb 26, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 26, 2025CVE 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=5.13
  2. Affected versionversion=b7cccd397f310739fb85383033e95580f99927e0 <0c8a8da182d4333d9bbb9131d765145568c847b2
  3. Affected versionversion=b7cccd397f310739fb85383033e95580f99927e0 <8cf6f98ab1d16d5e607635a0c21c4231eb15367e
  4. Affected versionversion=b7cccd397f310739fb85383033e95580f99927e0 <af47248407c0c5ae52a752af1ab5ce5b0db91502
  5. Affected versionversion=b7cccd397f310739fb85383033e95580f99927e0 <d62007edf01f5c11f75d0f4b1e538fc52a5b1982

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.13; version=b7cccd397f310739fb85383033e95580f99927e0 <0c8a8da182d4333d9bbb9131d765145568c847b2; version=b7cccd397f310739fb85383033e95580f99927e0 <8cf6f98ab1d16d5e607635a0c21c4231eb15367e; version=b7cccd397f310739fb85383033e95580f99927e0 <af47248407c0c5ae52a752af1ab5ce5b0db91502; version=b7cccd397f310739fb85383033e95580f99927e0 <d62007edf01f5c11f75d0f4b1e538fc52a5b1982

Published CVSS scores

7.8UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8Linux Kernel CNACVSS: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.

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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-416Use After Free
T1068Exploitation for Privilege Escalation

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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