CVE-2021-46972

Superblock shutdown disruption via leaked dentry reference

Published Feb 27, 2024 · Updated May 11, 2026

Resource leakage in Linux kernel overlayfs allows local users to disrupt superblock shutdown when an affected overlay is unmounted. In fs/overlayfs/namei.c, ovl_lookup() fails to call dput() for a temporary dentry when following a metacopy origin returns an error. The path requires local access that can exercise overlayfs and provoke the metacopy error; the leaked reference leaves dentries busy and triggers the kernel's unmount warning path.

CVSS severity5.5
Medium
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

Resource leakage in Linux kernel overlayfs allows local users to disrupt superblock shutdown when an affected overlay is unmounted. In fs/overlayfs/namei.c, ovl_lookup() fails to call dput() for a temporary dentry when following a metacopy origin returns an error. The path requires local access that can exercise overlayfs and provoke the metacopy error; the leaked reference leaves dentries busy and triggers the kernel's unmount warning path.

The record

CVE
CVE-2021-46972
Published
Feb 27, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-401, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 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=5.8
  2. Affected versionversion=6815f479ca90ee7fd2e28b2a420f796b974155fe <71d58457a8afc650da5d3292a7f7029317654d95
  3. Affected versionversion=6815f479ca90ee7fd2e28b2a420f796b974155fe <cf3e3330bc5719fa9d658e3e2f596bde89344a94
  4. Affected versionversion=6815f479ca90ee7fd2e28b2a420f796b974155fe <d587cfaef72b1b6f4b2774827123bce91f497cc8
  5. Affected versionversion=6815f479ca90ee7fd2e28b2a420f796b974155fe <eaab1d45cdb4bb0c846bd23c3d666d5b90af7b41

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.8; version=6815f479ca90ee7fd2e28b2a420f796b974155fe <71d58457a8afc650da5d3292a7f7029317654d95; version=6815f479ca90ee7fd2e28b2a420f796b974155fe <cf3e3330bc5719fa9d658e3e2f596bde89344a94; version=6815f479ca90ee7fd2e28b2a420f796b974155fe <d587cfaef72b1b6f4b2774827123bce91f497cc8; version=6815f479ca90ee7fd2e28b2a420f796b974155fe <eaab1d45cdb4bb0c846bd23c3d666d5b90af7b41

Published CVSS scores

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.

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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
T1499Endpoint Denial of Service

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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