ntfs: reject invalid sectors_per_cluster in the boot sector

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Summary

CVECVE-2026-98135
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 11:17:44 UTC
Updated2026-09-25 11:17:44 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ntfs: reject invalid sectors_per_cluster in the boot sector is_boot_sector_ntfs() checks the boot sector's sectors_per_cluster field with a range test that rejects 0x81..0xf3 but accepts 0 and other non-power-of-two counts. A zero value reaches parse_ntfs_boot_sector(): sectors_per_cluster_bits = ffs(sectors_per_cluster) - 1; ... vol->cluster_size = vol->sector_size << sectors_per_cluster_bits; ffs(0) is 0, so sectors_per_cluster_bits becomes (unsigned)-1 and the shift is undefined: UBSAN: shift-out-of-bounds in fs/ntfs/super.c:673:39 shift exponent 4294967295 is too large for 32-bit type 'int' This change rejects any non-power-of-two value, since it feeds the aforementioned shift via ffs() - 1, which only yields the correct shift for a power of two.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 6251f0b0de7d645e3591931ca4c11d8322c1866f 7524c3145a3bac92bebbc47a29c007f1d874c9b3 git Not specified
CNA Linux Linux affected 6251f0b0de7d645e3591931ca4c11d8322c1866f 323751a604e7533fa473874d999371592a614207 git Not specified
CNA Linux Linux affected 7.1 Not specified
CNA Linux Linux unaffected 7.1 semver Not specified
CNA Linux Linux unaffected 7.2.7 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7524c3145a3bac92bebbc47a29c007f1d874c9b3 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/323751a604e7533fa473874d999371592a614207 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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