GHSA-V762-VR2V-9263
Vulnerability from github – Published: 2026-06-24 12:30 – Updated: 2026-09-14 12:31In 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.
{
"affected": [],
"aliases": [
"CVE-2026-52944"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-24T10:17:19Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE\n\nFSCTL_SET_SPARSE in fsctl_set_sparse() modifies the file\u0027s sparse\nattribute and saves it through xattr without any permission checks.\n\nThis exposes two issues:\n\n1) A client on a read-only share can change the sparse attribute\n on files it opened, even though the share is read-only.\n Other FSCTL write operations already check\n test_tree_conn_flag(work-\u003etcon, KSMBD_TREE_CONN_FLAG_WRITABLE),\n but FSCTL_SET_SPARSE does not.\n\n2) Even on writable shares, clients without FILE_WRITE_DATA or\n FILE_WRITE_ATTRIBUTES access should not modify the sparse\n attribute. Similar handle-level checks exist in other functions\n but are missing here.\n\nAdd both share-level writable check and per-handle access check.\nUse goto out on error to avoid leaking file references.",
"id": "GHSA-v762-vr2v-9263",
"modified": "2026-09-14T12:31:30Z",
"published": "2026-06-24T12:30:31Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-52944"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3127a884525dc8ca4def73254bfcd3ccef0bf812"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3a9a0a1c38ef90788f5d7c4b29903c8b220f744a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/aef151bcfa494bfe983669de2726734b534adb73"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c5ab11263e3c89aa7989afc5374ef7743e092fd0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cc57232cae23c0df91b4a59d0f519141ce9b5b02"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/de9eb0b44fa9123170e6245b49638e0e453c10f8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ef664475c1bf1a27d45dae6848ca9c9c4d86853f"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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