CVE-2025-40307

Filesystem corruption via unchecked exFAT allocation bitmap

Published Dec 8, 2025 · Updated Aug 19, 2026

Improper input validation in Linux exFAT allows local users to corrupt data on a mounted crafted filesystem by creating a directory. The allocator trusts allocation-bitmap cluster bits without verifying that the bitmap's own clusters are marked in use, so exfat_mkdir can allocate and zero the live bitmap cluster. Reachability requires a crafted exFAT image mounted read-write and permission to create a directory; exploitation can disclose or overwrite co-resident files, delete directory entries, hang tasks, or render the volume unusable.

CVSS severity7.8
High
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Linux exFAT allows local users to corrupt data on a mounted crafted filesystem by creating a directory. The allocator trusts allocation-bitmap cluster bits without verifying that the bitmap's own clusters are marked in use, so exfat_mkdir can allocate and zero the live bitmap cluster. Reachability requires a crafted exFAT image mounted read-write and permission to create a directory; exploitation can disclose or overwrite co-resident files, delete directory entries, hang tasks, or render the volume unusable.

The record

CVE
CVE-2025-40307
Published
Dec 8, 2025
Updated
Aug 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1485
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 8, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 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=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf
  2. Affected versionversion=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <67ce8034dc0278ddd88cad93d4218a945180dddd
  3. Affected versionversion=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <6bc58b4c53795ab5fe00648344aa7d9d61175f90
  4. Affected versionversion=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <79c1587b6cda74deb0c86fc7ba194b92958c793c
  5. Affected versionversion=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <87f827d53bd0688597bda63ae95908e2ad39bac0
  6. Affected versionversion=5.7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf; version=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <67ce8034dc0278ddd88cad93d4218a945180dddd; version=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <6bc58b4c53795ab5fe00648344aa7d9d61175f90; version=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <79c1587b6cda74deb0c86fc7ba194b92958c793c; version=1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 <87f827d53bd0688597bda63ae95908e2ad39bac0; version=5.7

Published CVSS scores

7.8LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1485Data Destruction

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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