🛡️ CVE-2025-40307 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

exfat: validate cluster allocation bits of the allocation bitmap

In the Linux kernel, the following vulnerability has been resolved:

exfat: validate cluster allocation bits of the allocation bitmap

syzbot created an exfat image with cluster bits not set for the allocation

bitmap. exfat-fs reads and uses the allocation bitmap without checking

this. The problem is that if the start cluster of the allocation bitmap

is 6, cluster 6 can be allocated when creating a directory with mkdir.

exfat zeros out this cluster in exfat_mkdir, which can delete existing

entries. This can reallocate the allocated entries. In addition,

the allocation bitmap is also zeroed out, so cluster 6 can be reallocated.

This patch adds exfat_test_bitmap_range to validate that clusters used for

the allocation bitmap are correctly marked as in-use.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Affected software

CVE-2025-40307 is recorded against 2 packages.

  • kernel (from 6.13.0 up to 6.17.8)
  • unknown

Timeline and source

Published on 8 December 2025 and last revised on 6 August 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

CVE-2025-40307 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-12-08
Updated 2026-08-12
Modified 2026-08-06
Fix URL N/A

Affected Packages

Software From version Fixed in
kernel 6.13.0 6.17.8
unknown — —

Similar Threats

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