CVE-2021-47117

Local kernel crash via overlapping ext4 extents

Published Mar 15, 2024 · Updated May 11, 2026

Denial of service in the Linux kernel ext4 subsystem allows local users to crash the kernel through file operations after an extent split fails. The failure-recovery path can leave overlapping extents, which causes ext4_es_cache_extent to encounter an invariant violation and trigger a kernel BUG. Reachability requires local access to an ext4 filesystem and a split failure; ENOSPC and EDQUOT are identified as user-triggerable conditions.

CVSS severity5.5
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in the Linux kernel ext4 subsystem allows local users to crash the kernel through file operations after an extent split fails. The failure-recovery path can leave overlapping extents, which causes ext4_es_cache_extent to encounter an invariant violation and trigger a kernel BUG. Reachability requires local access to an ext4 filesystem and a split failure; ENOSPC and EDQUOT are identified as user-triggerable conditions.

The record

CVE
CVE-2021-47117
Published
Mar 15, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 15, 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

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=3.9
  2. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <082cd4ec240b8734a82a89ffb890216ac98fec68
  3. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <48105dc98c9ca35af418746277b087cb2bc6df7c
  4. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <569496aa3776eea1ff0d49d0174ac1b7e861e107
  5. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <5b3a9a2be59478b013a430ac57b0f3d65471b071
  6. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <920697b004e49cb026e2e15fe91be065bf0741b7
  7. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <d3b668b96ad3192c0581a248ae2f596cd054792a
  8. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <d8116743ef5432336289256b2f7c117299213eb9
  9. Affected versionversion=adb2355104b2109e06ba5276485d187d023b2fd2 <e33bafad30d34cfa5e9787cb099cab05e2677fcb

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.9; version=adb2355104b2109e06ba5276485d187d023b2fd2 <082cd4ec240b8734a82a89ffb890216ac98fec68; version=adb2355104b2109e06ba5276485d187d023b2fd2 <48105dc98c9ca35af418746277b087cb2bc6df7c; version=adb2355104b2109e06ba5276485d187d023b2fd2 <569496aa3776eea1ff0d49d0174ac1b7e861e107; version=adb2355104b2109e06ba5276485d187d023b2fd2 <5b3a9a2be59478b013a430ac57b0f3d65471b071; version=adb2355104b2109e06ba5276485d187d023b2fd2 <920697b004e49cb026e2e15fe91be065bf0741b7; version=adb2355104b2109e06ba5276485d187d023b2fd2 <d3b668b96ad3192c0581a248ae2f596cd054792a; version=adb2355104b2109e06ba5276485d187d023b2fd2 <d8116743ef5432336289256b2f7c117299213eb9; version=adb2355104b2109e06ba5276485d187d023b2fd2 <e33bafad30d34cfa5e9787cb099cab05e2677fcb

Published CVSS scores

5.5UbuntuCVSS:3.1/AV:L/AC:L/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.

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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.

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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