CVE-2023-54021

Kernel BUG via ext4 allocation underflow

Published Dec 24, 2025 · Updated Dec 24, 2025

Integer underflow in ext4 block allocation in Linux 2.6.25 and later allows attackers to trigger a kernel BUG during filesystem activity. The ext4_mb_normalize_request function can subtract an oversized request from ar->pright and pass the underflowed goal to ext4_get_group_no_and_offset. Reachability requires the normalization path to receive a size above the right preallocation boundary; public records do not establish whether the result is limited to task failure or extends to a kernel panic.

CVSS severityUnavailable
Unscored
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in ext4 block allocation in Linux 2.6.25 and later allows attackers to trigger a kernel BUG during filesystem activity. The ext4_mb_normalize_request function can subtract an oversized request from ar->pright and pass the underflowed goal to ext4_get_group_no_and_offset. Reachability requires the normalization path to receive a size above the right preallocation boundary; public records do not establish whether the result is limited to task failure or extends to a kernel panic.

The record

CVE
CVE-2023-54021
Published
Dec 24, 2025
Updated
Dec 24, 2025
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 24, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 24, 2025Record 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=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2479bb6cbdb4d56b807bbe5229e3e26a6f1f4530
  2. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <390eee955d4de4662db5e3e9e9a9eae020432cb7
  3. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3ca3005b502ca8ea87d6a344323b179b48c4e4a3
  4. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <abb330ffaa3a0ae7ce632e28c9260b461c01f19f
  5. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b07ffe6927c75d99af534d685282ea188d9f71a6
  6. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <bc4a3e1d07a86ae5845321d371190244acacb2f2
  7. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c6bee8970075b256fc1b07bf4873049219380818
  8. Affected versionversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cee78217a7ae72d11c2e21e1a5263b8044489823

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <2479bb6cbdb4d56b807bbe5229e3e26a6f1f4530; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <390eee955d4de4662db5e3e9e9a9eae020432cb7; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <3ca3005b502ca8ea87d6a344323b179b48c4e4a3; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <abb330ffaa3a0ae7ce632e28c9260b461c01f19f; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b07ffe6927c75d99af534d685282ea188d9f71a6; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <bc4a3e1d07a86ae5845321d371190244acacb2f2; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <c6bee8970075b256fc1b07bf4873049219380818; version=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <cee78217a7ae72d11c2e21e1a5263b8044489823

Published CVSS scores

No CVSS assessment is available in this record.

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)
VectorUnavailable
PrivilegesUnavailable
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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