CVE-2026-52944 (GCVE-0-2026-52944)

Vulnerability from cvelistv5 – Published: 2026-06-24 09:59 – Updated: 2026-06-24 09:59
VLAI
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < 3127a884525dc8ca4def73254bfcd3ccef0bf812 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < de9eb0b44fa9123170e6245b49638e0e453c10f8 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < aef151bcfa494bfe983669de2726734b534adb73 (git)
Affected: e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 , < cc57232cae23c0df91b4a59d0f519141ce9b5b02 (git)
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Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          "programFiles": [
            "fs/smb/server/smb2pdu.c"
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          "value": "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."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-06-24T09:59:09.149Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52944",
    "datePublished": "2026-06-24T09:59:09.149Z",
    "dateReserved": "2026-06-09T07:44:35.371Z",
    "dateUpdated": "2026-06-24T09:59:09.149Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-07-07",
      "epss": "0.00165",
      "percentile": "0.06015"
    },
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  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.