CVE-2026-52944
ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE
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.
INFO
Published Date :
June 24, 2026, 9:59 a.m.
Last Modified :
June 24, 2026, 9:59 a.m.
Remotely Exploit :
No
Source :
Linux
Affected Products
The following products are affected by CVE-2026-52944
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Add share-level writable check.
- Add per-handle access check for sparse attribute.
- Ensure file references are not leaked on error.
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