23 Oct 2026 15:48:27 UTC
ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE
cve-program · CVE-2026-52944 · Published
CVE-2026-52944
ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE
cve-program · severity unknownCVSS unknownCheck source for fixed versionsKEV status unknown
cve-program · CVE-2026-52944
PublishedIn 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.
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