CVE-2025-40307
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-12-08

Last updated on: 2025-12-08

Assigner: kernel.org

Description
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.
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Meta Information
Published
2025-12-08
Last Modified
2025-12-08
Generated
2026-06-16
AI Q&A
2025-12-08
EPSS Evaluated
2026-06-15
NVD
CVE-2025-40307
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux kernel *
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Exploitability
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CWE ID Description
CWE-UNKNOWN
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Executive Summary

This vulnerability in the Linux kernel's exfat filesystem involves improper validation of cluster allocation bits in the allocation bitmap. Specifically, the exfat filesystem reads and uses the allocation bitmap without verifying that clusters used for the allocation bitmap are correctly marked as in-use. This can lead to cluster 6 being allocated when creating a directory, which causes exfat to zero out that cluster and the allocation bitmap, potentially deleting existing directory entries and allowing reallocation of allocated entries.

Impact Analysis

The vulnerability can lead to data corruption or loss because existing directory entries may be deleted when cluster 6 is zeroed out during directory creation. This can cause reallocation of clusters that should not be reallocated, potentially resulting in loss or corruption of files stored on the exfat filesystem.

Mitigation Strategies

The vulnerability has been resolved by a patch that adds validation of the allocation bitmap clusters in the exfat filesystem driver. Immediate steps should include updating the Linux kernel to a version that includes this patch to ensure the allocation bitmap is properly validated and prevent potential data corruption or reallocation issues.

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