CVE-2026-98135 ntfs: reject invalid sectors_per_cluster in the boot sector

What is CVE-2026-98135?

CVE-2026-98135 is a medium-severity vulnerability in Linux kernel, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Which versions are affected by CVE-2026-98135?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-98135?

Apply the vendor's patch.

Is CVE-2026-98135 being exploited?

There is no known exploitation of CVE-2026-98135 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-98135, GHSA-vhjh-88x6-7w6p, UBUNTU-CVE-2026-98135.