CVE-2026-52944 Details
Description
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.
A vulnerability in the Linux kernel's ksmbd component allows for a permission bypass related to the FSCTL_SET_SPARSE operation. This vulnerability is present in the stable branch of the Linux kernel. The issue arises because FSCTL_SET_SPARSE modifies a file's sparse attribute and saves it via extended attributes without performing any permission checks. As a result, two problems emerge: first, a client on a read-only share can alter the sparse attribute of files it has opened, despite the share being read-only. While other FSCTL write operations verify if the share is writable, FSCTL_SET_SPARSE does not. Second, even on writable shares, clients lacking FILE_WRITE_DATA or FILE_WRITE_ATTRIBUTES access should not be able to change the sparse attribute. Although similar checks are implemented in other functions, they are absent here.
Users can update to the latest version of the Linux kernel where this vulnerability has been addressed. Instructions for downloading the patched version are available on the Linux Kernel Archives.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| NVD-CWE-noinfo | Insufficient Information to Classify Weakness | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 5.15, < 6.6.143 >= 6.7, < 6.18.35 >= 6.19, < 7.0.12 7.1 rc1 7.1 rc2 7.1 rc3 7.1 rc4 7.1 rc5 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 14, 2026 | CVE Modified | kernel.org |
| Jul 8, 2026 | Initial Analysis | [email protected] |
| Jun 24, 2026 | New CVE Received | kernel.org |