Linux Kernel up to 7.2.6/7.3-rc1 NTFS ntfs_cluster_free_from_rl_nolock free_clusters calculation

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc1. It has been rated as very critical. Affected is the function ntfs_cluster_free_from_rl_nolock of the component NTFS. This manipulation of the argument free_clusters causes calculation. The identification of this vulnerability is CVE-2026-98139. The attack can only be executed locally. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.6/7.3-rc1. Affected by this vulnerability is the function ntfs_cluster_free_from_rl_nolock of the component NTFS. The manipulation of the argument free_clusters with an unknown input leads to a calculation vulnerability. The CWE definition for the vulnerability is CWE-682. The product performs a calculation that generates incorrect or unintended results that are later used in security-critical decisions or resource management. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ntfs: only count successfully cleared runs when freeing clusters ntfs_cluster_free_from_rl_nolock() adds a run's length to nr_freed whenever the error bookkeeping condition is false, which includes cases where ntfs_bitmap_clear_run() actually failed - e.g. a second run failing with the same errno as an earlier one, or any failure after a non-ENOMEM error was already recorded. Since a failed ntfs_bitmap_clear_run() rolls back its partial modifications, no bits were cleared for that run, yet its length still inflates vol->free_clusters, corrupting statfs output and the allocator's free space gate. Only count runs whose bitmap clear succeeded.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-98139 since 09/25/2026. The exploitation appears to be easy. An attack has to be approached locally. Technical details are known, but no exploit is available. The price for an exploit might be around 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 7eb97d8828e7758b9c81277f7802e740a800f78a/be9e89ccb8e52a3e4b67feeb03ebd8133091dc7e is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion