CVE-2026-89614

/// Technical description

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

ntfs: bound the free-cluster bitmap scan to the volume

vol->lcn_empty_bits_per_page is sized from vol->nr_clusters at mount, but

ntfs_cluster_alloc() bounds its scan of that array by the size of $Bitmap.

Those are independent on-disk quantities and the mount-time check only

rejects a $Bitmap that is too small, so an image whose $Bitmap covers more

clusters than the volume has lets the scan index past the array. A run

whose LCN lies in that gap takes the allocator straight there, since the

caller passes the file's own last LCN as its locality hint. KASAN reports

a slab out-of-bounds read when a file on such a volume is extended.

Clamp the scan to what that array covers, mirroring the max_index

calculation the mount-time scan already uses, and reject a decoded LCN

at or beyond nr_clusters in the mapping pairs decoder. Conforming

volumes are unaffected.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References