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ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE

Type: advisorySources: OSV

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.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.15.221, 6.1.188, 6.12.110, 6.18.35, 6.6.143, 7.0.12
CVEs
CVE-2026-52944
Confirmed fixed CVEs
Not specified
Updated in this feed
6 Nov 2026, 18:38 UTC · Revision 1

Source evidence

ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE

core-osv · Original source

Published 24 Jun 2026, 09:59 UTC

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.

osv:CVE-2026-52944

Kernel

Fixed versions: 5.15.221, 6.1.188, 6.6.143, 6.12.110, 6.18.35, 7.0.12

Complete source record
{
  "id": "e2163d68c47bf1794e7fba1fcf6d76d131f19bd7b0d960ff814b70010c48ac20",
  "url": "https://osv.dev/vulnerability/CVE-2026-52944",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE",
    "summary": "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.",
    "evidence": "osv:CVE-2026-52944",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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          {
            "value": "7.0.12",
            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    "severity": "unknown",
    "structured": {
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      "aliases": [
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      "affected": [
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        {
          "ranges": [
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            {
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                  "introduced": "6.7.0"
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              ]
            },
            {
              "type": "ECOSYSTEM",
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                  "introduced": "6.13.0"
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            {
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                  "introduced": "6.19.0"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
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        }
      ],
      "modified": "2026-10-28T02:30:47.910007884Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3127a884525dc8ca4def73254bfcd3ccef0bf812",
        "https://git.kernel.org/stable/c/3a9a0a1c38ef90788f5d7c4b29903c8b220f744a",
        "https://git.kernel.org/stable/c/aef151bcfa494bfe983669de2726734b534adb73",
        "https://git.kernel.org/stable/c/c5ab11263e3c89aa7989afc5374ef7743e092fd0",
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        "https://git.kernel.org/stable/c/de9eb0b44fa9123170e6245b49638e0e453c10f8",
        "https://git.kernel.org/stable/c/ef664475c1bf1a27d45dae6848ca9c9c4d86853f",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52944.json",
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        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52944.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-52944",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 515897,
  "published_at": "2026-06-24T09:59:09.149+00:00"
}