CVE-2026-64399 (GCVE-0-2026-64399)
Vulnerability from cvelistv5
Published
2026-07-25 08:50
Modified
2026-08-17 04:54
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE The FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the destination file's data via vfs_clone_file_range() with neither the share-level KSMBD_TREE_CONN_FLAG_WRITABLE check nor a per-handle fp->daccess check that the other write-bearing arms carry. A client can overwrite destination data on a read-only share, or from a handle opened with only FILE_WRITE_ATTRIBUTES (which still yields an FMODE_WRITE filp). FILE_WRITE_ATTRIBUTES-only destination handle overwrote the file's data via the clone. Add both checks, matching the FSCTL_SET_SPARSE permission fix; require FILE_WRITE_DATA since this writes data.
References
Impacted products
Vendor Product Version
Linux Linux Version: eb817368f50c1cbe1bd07044124aad7db6330e3a
Version: eb817368f50c1cbe1bd07044124aad7db6330e3a
Version: eb817368f50c1cbe1bd07044124aad7db6330e3a
Version: eb817368f50c1cbe1bd07044124aad7db6330e3a
Version: eb817368f50c1cbe1bd07044124aad7db6330e3a
Version: eb817368f50c1cbe1bd07044124aad7db6330e3a
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{
  "containers": {
    "cna": {
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          "programFiles": [
            "fs/smb/server/smb2pdu.c"
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              "version": "6.18.39",
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              "version": "7.1.4",
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            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.178",
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE\n\nThe FSCTL_DUPLICATE_EXTENTS_TO_FILE arm of smb2_ioctl() overwrites the\ndestination file\u0027s data via vfs_clone_file_range() with neither the\nshare-level KSMBD_TREE_CONN_FLAG_WRITABLE check nor a per-handle\nfp-\u003edaccess check that the other write-bearing arms carry. A client can\noverwrite destination data on a read-only share, or from a handle opened\nwith only FILE_WRITE_ATTRIBUTES (which still yields an FMODE_WRITE filp).\nFILE_WRITE_ATTRIBUTES-only destination handle overwrote the file\u0027s data via\nthe clone. Add both checks, matching the FSCTL_SET_SPARSE permission fix;\nrequire FILE_WRITE_DATA since this writes data."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - An attacker reaches smb2_ioctl() remotely through ksmbd\u2019s SMB service on TCP port 445.\nAC:L - The attacker directly controls both file handles, offsets, length, and request timing; no race or uncontrollable condition is required on a clone-capable filesystem.\nPR:N - A passwordless guest session on a guest-enabled share can obtain the required session, tree connection, and file handles without credentials.\nUI:N - The attacker independently negotiates the SMB session, opens the files, and submits the malicious IOCTL without victim action.\nS:U - The unauthorized file modification and any resulting code execution remain within the host kernel and services governed by the same security authority.\nC:H - In a plausible share containing service-loaded code or configuration, attacker-controlled extent replacement can yield code execution and consequent access to sensitive data.\nI:H - The attacker can overwrite arbitrary destination ranges with chosen source data despite a read-only share or a handle lacking FILE_WRITE_DATA.\nA:H - Repeated or complete corruption of critical files, databases, executables, or service configuration can cause a persistent loss of the affected system or service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:54:56.640Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/bf460ad5958d506492de4524a656439da3f99c51"
        },
        {
          "url": "https://git.kernel.org/stable/c/620d133d469295ee7c017ca6aafac335f65c4a5a"
        },
        {
          "url": "https://git.kernel.org/stable/c/9b9cf7e65cbeaae1b6636144bacee611cdd7a5d6"
        },
        {
          "url": "https://git.kernel.org/stable/c/baae7b39673ec21073a25e3d14f8feaada01d5df"
        },
        {
          "url": "https://git.kernel.org/stable/c/c917e4522d251071dde9871b9142d8ea1186ebfe"
        },
        {
          "url": "https://git.kernel.org/stable/c/388e4139db27a9e3612c9d356b826f5b1ff6a9e3"
        }
      ],
      "title": "ksmbd: add permission checks for FSCTL_DUPLICATE_EXTENTS_TO_FILE",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64399",
    "datePublished": "2026-07-25T08:50:42.925Z",
    "dateReserved": "2026-07-19T15:36:31.785Z",
    "dateUpdated": "2026-08-17T04:54:56.640Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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