CVE-2021-47365

Local denial of service via AFS page leak

Published May 21, 2024 · Updated May 11, 2026

Incomplete cleanup in the AFS writeback path in Linux 5.13 through 5.14.8 allows local users to exhaust memory through AFS writes. An early exit from afs_extend_writeback() retains a speculative page reference instead of releasing it after xarray scanning finds a page that cannot be written immediately. Exploitation requires local low-privileged access and repeated triggering can consume roughly 4 GiB per run, interrupting the host.

CVSS severity5.5
Medium
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incomplete cleanup in the AFS writeback path in Linux 5.13 through 5.14.8 allows local users to exhaust memory through AFS writes. An early exit from afs_extend_writeback() retains a speculative page reference instead of releasing it after xarray scanning finds a page that cannot be written immediately. Exploitation requires local low-privileged access and repeated triggering can consume roughly 4 GiB per run, interrupting the host.

The record

CVE
CVE-2021-47365
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-459, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 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=e87b03f5830ecd8ca21836d3ee48c74f8d58fa31 <581b2027af0018944ba301d68e7af45c6d1128b5
  3. Affected versionversion=e87b03f5830ecd8ca21836d3ee48c74f8d58fa31 <d130b5fdd42254d92948d06347940276140c927e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.13; version=e87b03f5830ecd8ca21836d3ee48c74f8d58fa31 <581b2027af0018944ba301d68e7af45c6d1128b5; version=e87b03f5830ecd8ca21836d3ee48c74f8d58fa31 <d130b5fdd42254d92948d06347940276140c927e

Published CVSS scores

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

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-459Incomplete Cleanup
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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