CVE-2021-47452Public exploit

Kernel warning via duplicate base-hook unregistration

Published May 22, 2024 · Updated May 23, 2026

Improper hook cleanup in affected Linux kernels allows local users to trigger a harmless warning during network namespace removal. The nf_tables netdev notifier processes an UNREGISTER event after the core pre_exit hook has already removed the same base hook, causing a second unregistration attempt. Reaching it requires local access to create a bridge, an nftables netdev table and ingress chain, and then remove the namespace; the CNA reports no crash or data impact.

CVSS severity5.5
Medium
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper hook cleanup in affected Linux kernels allows local users to trigger a harmless warning during network namespace removal. The nf_tables netdev notifier processes an UNREGISTER event after the core pre_exit hook has already removed the same base hook, causing a second unregistration attempt. Reaching it requires local access to create a bridge, an nftables netdev table and ingress chain, and then remove the namespace; the CNA reports no crash or data impact.

The record

CVE
CVE-2021-47452
Published
May 22, 2024
Updated
May 23, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 22, 2024CVE publishedPublication date reported by the CVE source.
  2. May 23, 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=0a0e5d47670b753d3dbf88f3c77a97a30864d9bd
  2. Affected versionversion=5.10.17 <5.11
  3. Affected versionversion=5.11
  4. Affected versionversion=5.4.99 <5.5
  5. Affected versionversion=767d1216bff82507c945e92fe719dff2083bb2f4 <68a3765c659f809dcaac20030853a054646eb739
  6. Affected versionversion=767d1216bff82507c945e92fe719dff2083bb2f4 <90c7c58aa2bd02c65a4c63b7dfe0b16eab12cf9f
  7. Affected versionversion=b110391d1e806167254d3c7ae5d637191d913175

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0a0e5d47670b753d3dbf88f3c77a97a30864d9bd; version=5.10.17 <5.11; version=5.11; version=5.4.99 <5.5; version=767d1216bff82507c945e92fe719dff2083bb2f4 <68a3765c659f809dcaac20030853a054646eb739; version=767d1216bff82507c945e92fe719dff2083bb2f4 <90c7c58aa2bd02c65a4c63b7dfe0b16eab12cf9f; version=b110391d1e806167254d3c7ae5d637191d913175

Published CVSS scores

5.5NVDCVSS: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 exploitPublished

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

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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