CVE Catalog

CVE-2026-52944

MediumCVSS 5.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.12%

2th percentile - higher than 2% of all known CVEs

Summary

In the Linux kernel's ksmbd (SMB) filesystem, a missing access control for FSCTL_SET_SPARSE was found. The fsctl_set_sparse() function modifies the sparse attribute of a file without checking if the share is read-only or if the client has proper permissions (FILE_WRITE_DATA or FILE_WRITE_ATTRIBUTES).

Risk Assessment

The organization is at risk of unauthorized file attribute modification by users with read-only access or insufficient rights, potentially leading to data integrity breaches and security policy violations.

Recommendation

Immediately update the Linux kernel to a version containing the fix (commit adding permission checks for FSCTL_SET_SPARSE). Until the update, restrict SMB share access to trusted clients.

Other vulnerabilities in Linux kernel

See all
Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS