Review reviewHigh

CVE-2025-40307

Linux

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 ou...

CVSS: 7.8
EPSS: 0.14%
CISA KEV: Not listed
Published: 2025.12.08

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.14%

Technical severityCVSS 7.8

Vulnerability overview

Affected product and versions

Product: Linux
Affected versions: >= 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 < 67ce8034dc0278ddd88cad93d4218a945180dddd, >= 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 < 6bc58b4c53795ab5fe00648344aa7d9d61175f90, >= 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 < 13c1d24803d5b0446b3f6f0fdd67e07ac1fdc7bf, >= 1acf1a564b6034b5af1e7fb23cb98cb3bb4f6003 < 79c1587b6cda74deb0c86fc7ba194b92958c793c, >= 5.7
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that Linux and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE: Not available