CVE-2021-47406

System hang via unchecked ext4 mapping failure

Published May 21, 2024 · Updated May 11, 2026

An infinite loop in the Linux ext4 fast-commit replay path allows local users to hang the system with a corrupted file system. ext4_ext_replay_set_iblocks fails to stop when ext4_map_blocks returns an error, so replay repeats without progress. The condition requires inline_data and fast_commit to be enabled and corruption to be encountered during journal replay; the observed consequence is a tight-loop host lockup.

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

An infinite loop in the Linux ext4 fast-commit replay path allows local users to hang the system with a corrupted file system. ext4_ext_replay_set_iblocks fails to stop when ext4_map_blocks returns an error, so replay repeats without progress. The condition requires inline_data and fast_commit to be enabled and corruption to be encountered during journal replay; the observed consequence is a tight-loop host lockup.

The record

CVE
CVE-2021-47406
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
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=5.10
  2. Affected versionversion=8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 <1fd95c05d8f742abfe906620780aee4dbe1a2db0
  3. Affected versionversion=8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 <27e10c5d31ff1d222c7f797f1ee96d422859ba67
  4. Affected versionversion=8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 <a63474dbf692dd09b50fed592bc41f6de5f102fc

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.10; version=8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 <1fd95c05d8f742abfe906620780aee4dbe1a2db0; version=8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 <27e10c5d31ff1d222c7f797f1ee96d422859ba67; version=8016e29f4362e285f0f7e38fadc61a5b7bdfdfa2 <a63474dbf692dd09b50fed592bc41f6de5f102fc

Published CVSS scores

5.5CISACVSS: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

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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