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.
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| Vendors | Products |
|---|---|
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Linux
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Linux Kernel
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Solution
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Workaround
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Fri, 25 Sep 2026 12:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-680 CWE-788 |
Fri, 25 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In 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. | |
| Title | ntfs: reject invalid sectors_per_cluster in the boot sector | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-25T10:36:13.510Z
Reserved: 2026-09-25T10:25:14.319Z
Link: CVE-2026-98135
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-25T11:17:44.933
Modified: 2026-09-25T11:17:44.933
Link: CVE-2026-98135
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-09-25T13:30:18Z