Linux Kernel up to 7.2.6/7.3-rc1 ntfs fs/ntfs/super.c parse_ntfs_boot_sector sectors_per_cluster out-of-bounds

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc1 and classified as very critical. The impacted element is the function parse_ntfs_boot_sector of the file fs/ntfs/super.c of the component ntfs. Executing a manipulation of the argument sectors_per_cluster can lead to out-of-bounds. This vulnerability is handled as CVE-2026-98135. The attack can be executed remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc1. It has been declared as very critical. This vulnerability affects the function parse_ntfs_boot_sector of the file fs/ntfs/super.c of the component ntfs. The manipulation of the argument sectors_per_cluster with an unknown input leads to a out-of-bounds vulnerability. The CWE definition for the vulnerability is CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-98135 since 09/25/2026. The exploitation appears to be easy. The attack can be initiated remotely. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 09/25/2026).

Upgrading to version 7.2.7 or 7.3-rc2 eliminates this vulnerability. Applying the patch 7524c3145a3bac92bebbc47a29c007f1d874c9b3/323751a604e7533fa473874d999371592a614207 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.3-rc1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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