CVE-2021-47492

Kernel compromise via writeback page use-after-free

Published May 22, 2024 · Updated Aug 5, 2026

Use-after-free in Linux kernel collapse_file allows local users to compromise the kernel through executable mappings on XFS. collapse_file frees a page that is still under writeback because its indirect page_has_private check misses XFS filesystems whose block size is at least the system page size. An unprivileged local process can exercise the path through MADV_HUGEPAGE retries, causing a kernel panic or enabling kernel-memory read, write, and control-flow primitives.

CVSS severity7.8
High
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

Use-after-free in Linux kernel collapse_file allows local users to compromise the kernel through executable mappings on XFS. collapse_file frees a page that is still under writeback because its indirect page_has_private check misses XFS filesystems whose block size is at least the system page size. An unprivileged local process can exercise the path through MADV_HUGEPAGE retries, causing a kernel panic or enabling kernel-memory read, write, and control-flow primitives.

The record

CVE
CVE-2021-47492
Published
May 22, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068, T1499.004
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.4
  2. Affected versionversion=99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 <5e669d8ab30ab61dec3c36e27b4711f07611e6fc
  3. Affected versionversion=99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 <69a7fa5cb0de06c8956b040f19a7248c8c8308ca
  4. Affected versionversion=99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 <74c42e1baacf206338b1dd6b6199ac964512b5bb

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.4; version=99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 <5e669d8ab30ab61dec3c36e27b4711f07611e6fc; version=99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 <69a7fa5cb0de06c8956b040f19a7248c8c8308ca; version=99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 <74c42e1baacf206338b1dd6b6199ac964512b5bb

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8kernel.orgCVSS: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.

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

T1068Exploitation for Privilege Escalation
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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