Linux Kernel up to 6.6.142/6.18.34/7.0.11 ksmbd fsctl_set_sparse permission

Summaryinfo

A vulnerability described as critical has been identified in Linux Kernel up to 6.6.142/6.18.34/7.0.11. This affects the function fsctl_set_sparse of the component ksmbd. Such manipulation of the argument sparse leads to permission. This vulnerability is listed as CVE-2026-52944. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.6.142/6.18.34/7.0.11. It has been rated as critical. Affected by this issue is the function fsctl_set_sparse of the component ksmbd. The manipulation of the argument sparse with an unknown input leads to a permission vulnerability. Using CWE to declare the problem leads to CWE-275. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE FSCTL_SET_SPARSE in fsctl_set_sparse() modifies the file's sparse attribute and saves it through xattr without any permission checks. This exposes two issues: 1) A client on a read-only share can change the sparse attribute on files it opened, even though the share is read-only. Other FSCTL write operations already check test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE), but FSCTL_SET_SPARSE does not. 2) Even on writable shares, clients without FILE_WRITE_DATA or FILE_WRITE_ATTRIBUTES access should not modify the sparse attribute. Similar handle-level checks exist in other functions but are missing here. Add both share-level writable check and per-handle access check. Use goto out on error to avoid leaking file references.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-52944 since 06/09/2026. The exploitation is known to be easy. 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 06/24/2026). This vulnerability is assigned to T1222 by the MITRE ATT&CK project.

Upgrading to version 6.6.143, 6.18.35 or 7.0.12 eliminates this vulnerability. Applying the patch 3127a884525dc8ca4def73254bfcd3ccef0bf812/de9eb0b44fa9123170e6245b49638e0e453c10f8/aef151bcfa494bfe983669de2726734b534adb73/cc57232cae23c0df91b4a59d0f519141ce9b5b02 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. 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

• 6.6.142
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9
• 7.0.10
• 7.0.11

License

• open-source

Website

• Vendor: https://www.kernel.org/

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