CVE-2025-40307

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.

CVSS 3.1

7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

0.1% chance of exploitation in the next 30 days; higher than 3% of CVEs (scores of 2026-10-25)

Published

2025-12-08

Modified

2026-10-15

Record from

the NVD, synced 2026-10-19

References

• https://git.kernel.org/stable/c/13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf
• https://git.kernel.org/stable/c/67ce8034dc0278ddd88cad93d4218a945180dddd
• https://git.kernel.org/stable/c/6bc58b4c53795ab5fe00648344aa7d9d61175f90
• https://git.kernel.org/stable/c/79c1587b6cda74deb0c86fc7ba194b92958c793c
• https://git.kernel.org/stable/c/87f827d53bd0688597bda63ae95908e2ad39bac0

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