CVE-2026-68083 (GCVE-0-2026-68083)
Vulnerability from cvelistv5
Published
2026-08-10 11:41
Modified
2026-10-30 12:28
Severity ?
9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix path resolution in ksmbd_vfs_kern_path_create The SMB2 open lookup is rooted at the share with LOOKUP_BENEATH, but the create/mkdir/hardlink sink is not: ksmbd_vfs_kern_path_create() builds an absolute path with convert_to_unix_name() and resolves it from AT_FDCWD via start_creating_path(), so a ".." component is walked from the real filesystem root and escapes the export. An authenticated client races a missing path component so the rooted open lookup returns -ENOENT (taking the create branch) while the same component is present (a directory) when the create walk runs; the create then resolves ".." out of the share. Root the create walk at the share like the lookup and rename paths already are: resolve the parent with vfs_path_parent_lookup(..., LOOKUP_BENEATH, &share_conf->vfs_path) and create the final component with start_creating_noperm(). convert_to_unix_name() then has no callers and is removed.
References
Impacted products
Vendor Product Version
Linux Linux Version: 265fd1991c1db85fbabaad4946ca0e63e2ae688d
Version: 265fd1991c1db85fbabaad4946ca0e63e2ae688d
Version: 265fd1991c1db85fbabaad4946ca0e63e2ae688d
Version: 265fd1991c1db85fbabaad4946ca0e63e2ae688d
Version: 265fd1991c1db85fbabaad4946ca0e63e2ae688d
Version: 265fd1991c1db85fbabaad4946ca0e63e2ae688d
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/misc.c",
            "fs/smb/server/misc.h",
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          "programFiles": [
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            "fs/smb/server/misc.h",
            "fs/smb/server/vfs.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
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            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.40",
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            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.191",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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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: fix path resolution in ksmbd_vfs_kern_path_create\n\nThe SMB2 open lookup is rooted at the share with LOOKUP_BENEATH, but the\ncreate/mkdir/hardlink sink is not: ksmbd_vfs_kern_path_create() builds an\nabsolute path with convert_to_unix_name() and resolves it from AT_FDCWD\nvia start_creating_path(), so a \"..\" component is walked from the real\nfilesystem root and escapes the export.\n\nAn authenticated client races a missing path component so the rooted open\nlookup returns -ENOENT (taking the create branch) while the same component\nis present (a directory) when the create walk runs; the create then\nresolves \"..\" out of the share.\n\nRoot the create walk at the share like the lookup and rename paths already\nare: resolve the parent with vfs_path_parent_lookup(..., LOOKUP_BENEATH,\n\u0026share_conf-\u003evfs_path) and create the final component with\nstart_creating_noperm(). convert_to_unix_name() then has no callers and is\nremoved."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.1,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ksmbd is the in-kernel SMB server on TCP/445; the flaw is reached from remote SMB2_CREATE (and SMB2_SET_INFO hardlink) requests processed in ksmbd_conn_handler_loop() through smb2_open()/smb2_create_link() into ksmbd_vfs_kern_path_create().\nAC:L - Exploitation requires a TOCTOU race, but the attacker controls both sides by issuing concurrent SMB2_CREATE and directory-creation requests over one or more connections, so success does not depend on conditions outside attacker influence.\nPR:N - SMB2_CREATE requires a valid session, tree connect, and writable share, but ksmbd supports guest/anonymous sessions on writable exports; per kernel CNA precedent, export write access alone is not elevated privilege.\nUI:N - No victim interaction is required; the attacker sends crafted SMB2 protocol requests directly to a reachable ksmbd service without needing another user to mount shares or open files.\nS:U - Impact is confined to the host kernel filesystem namespace managed by ksmbd; escaping an SMB export is not a VM, IOMMU, or separate security-authority boundary crossing.\nC:N - This is a path-resolution logic flaw with no memory corruption, out-of-bounds access, or demonstrated arbitrary read of host files outside the export; impact is unauthorized creation/linking, not information disclosure.\nI:H - ksmbd_vfs_kern_path_create() resolves attacker paths from AT_FDCWD without LOOKUP_BENEATH, letting authenticated clients create files, directories, or hardlinks outside the exported share using the server\u0027s filesystem credentials.\nA:H - Repeated successful escaped creates/mkdirs outside the export can exhaust root-filesystem inodes or storage (especially tmpfs/world-writable targets), causing system-wide service unavailability on affected NAS/cloud hosts."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-30T12:28:02.157Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f1f53dc95edfb3d2072e5e8cd8eb9a2fe7d7f2d0"
        },
        {
          "url": "https://git.kernel.org/stable/c/a2516be69048856e2a49a51e00975dc59431f95c"
        },
        {
          "url": "https://git.kernel.org/stable/c/489d1ded01425c0fb33418172c0e4e588467526b"
        },
        {
          "url": "https://git.kernel.org/stable/c/c7c884a1305aa4540eb7942a50bd356b34120e1f"
        },
        {
          "url": "https://git.kernel.org/stable/c/98185b3025beeae92d1fe700d5db26b9ac4bf025"
        },
        {
          "url": "https://git.kernel.org/stable/c/1c8951963d8ed357f70f59e0ad4ddce2199d2016"
        }
      ],
      "title": "ksmbd: fix path resolution in ksmbd_vfs_kern_path_create",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-68083",
    "datePublished": "2026-08-10T11:41:47.153Z",
    "dateReserved": "2026-07-30T09:28:09.367Z",
    "dateUpdated": "2026-10-30T12:28:02.157Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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