CVE-2024-40955

Kernel crash via oversized ext4 group preallocation

Published Jul 12, 2024 · Updated May 11, 2026

A slab out-of-bounds read in Linux 6.5 through 6.6.35 and 6.7 through 6.9.6 allows local users to crash the kernel. The ext4 allocator derives index 29 from an oversized s_mb_group_prealloc value and reads a 14-entry s_mb_avg_fragment_size array without bounding that index. Triggering requires local access to write the ext4 sysfs parameter on a mounted filesystem and then force block allocation; the bounded consequence is a kernel crash.

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

A slab out-of-bounds read in Linux 6.5 through 6.6.35 and 6.7 through 6.9.6 allows local users to crash the kernel. The ext4 allocator derives index 29 from an oversized s_mb_group_prealloc value and reads a 14-entry s_mb_avg_fragment_size array without bounding that index. Triggering requires local access to write the ext4 sysfs parameter on a mounted filesystem and then force block allocation; the bounded consequence is a kernel crash.

The record

CVE
CVE-2024-40955
Published
Jul 12, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 12, 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=6.5
  2. Affected versionversion=7e170922f06bf46effa7c57f6035fc463d6edc7e <13df4d44a3aaabe61cd01d277b6ee23ead2a5206
  3. Affected versionversion=7e170922f06bf46effa7c57f6035fc463d6edc7e <677ff4589f1501578fa903a25bb14831d0607992
  4. Affected versionversion=7e170922f06bf46effa7c57f6035fc463d6edc7e <b829687ae1229224262bcabf49accfa2dbf8db06

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=6.5; version=7e170922f06bf46effa7c57f6035fc463d6edc7e <13df4d44a3aaabe61cd01d277b6ee23ead2a5206; version=7e170922f06bf46effa7c57f6035fc463d6edc7e <677ff4589f1501578fa903a25bb14831d0607992; version=7e170922f06bf46effa7c57f6035fc463d6edc7e <b829687ae1229224262bcabf49accfa2dbf8db06

Published CVSS scores

5.5CanonicalCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.4SUSECVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

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-125Out-of-bounds Read
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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