CVE-2025-40265

Kernel panic via unchecked block-size failure

Published Dec 4, 2025 · Updated May 11, 2026

Unchecked return handling in Linux 6.15 through 6.17.9 allows local users to crash the kernel by mounting crafted vfat media. In fs/fat/inode.c, fat_fill_super continues after sb_min_blocksize fails, allowing an unsupported 8 KiB block size to reach buffer allocation and trigger a kernel BUG. Exploitation requires high local privileges and an unformatted 8 KiB-block NVMe device, and the bounded consequence is 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

Unchecked return handling in Linux 6.15 through 6.17.9 allows local users to crash the kernel by mounting crafted vfat media. In fs/fat/inode.c, fat_fill_super continues after sb_min_blocksize fails, allowing an unsupported 8 KiB block size to reach buffer allocation and trigger a kernel BUG. Exploitation requires high local privileges and an unformatted 8 KiB-block NVMe device, and the bounded consequence is a kernel panic.

The record

CVE
CVE-2025-40265
Published
Dec 4, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-252, T1499.004
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Dec 4, 2025CVE 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=6.15
  2. Affected versionversion=a64e5a596067bddba87fcc2ce37e56c3fca831b7 <63b5aa01da0f38cdbd97d021477258e511631497
  3. Affected versionversion=a64e5a596067bddba87fcc2ce37e56c3fca831b7 <ee767b99b0045be286cceb8265bd4c9831be671e

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linuxversion=6.15; version=a64e5a596067bddba87fcc2ce37e56c3fca831b7 <63b5aa01da0f38cdbd97d021477258e511631497; version=a64e5a596067bddba87fcc2ce37e56c3fca831b7 <ee767b99b0045be286cceb8265bd4c9831be671e

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-252Unchecked Return Value
T1499.004Application or System Exploitation DoS

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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