NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers

{
  "id": "6d118ab20483c1be0f67bd257f3fc48e099d46f5cdfb4f1d23647f7c6e098195",
  "url": "https://osv.dev/vulnerability/CVE-2026-90149",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: NFSv4/flexfiles: fix NULL dereference for NFSv4.0 data servers flexfiles accepts NFSv4.0 data servers, but two NFSv4 code paths assume the data server client has a session. Unlike NFSv4.1+, an NFSv4.0 client has no session (clp->cl_session is NULL; it uses clp->cl_slot_tbl), so I/O to a v4.0 flexfiles DS oopses: - nfs4_init_ds_session() dereferences clp->cl_session->session_state while seeding the DS lease. It also only seeds cl_lease_time when NFS4_SESSION_INITING is set; without a session that never happens, so cl_lease_time stays 0 and nfs4_renew_state() busy-loops, requeuing every 5 seconds. Seed the lease whenever there is no session and return before touching session state. - ff_layout_async_handle_error_v4() dereferences clp->cl_session->fc_slot_table on every DS I/O error. Fall back to the v4.0 transport slot table (clp->cl_slot_tbl) when there is no session.",
    "evidence": "osv:CVE-2026-90149",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.191",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.18.52",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-90149",
      "aliases": [
        "CVE-2026-90149"
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      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
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                  "fixed": "336b6da10021c69a8f273bbacdf7432fdc89a06f"
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                  "fixed": "5527af72b0100c94287bfec901b6313eeac567ca"
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                  "fixed": "163c16e01f53fc8eb8d0f3484ae6c382265ecbbd"
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                {
                  "fixed": "436a214514e24103159aea455147d58b44a8a585"
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                  "fixed": "2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc"
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              "type": "ECOSYSTEM",
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            "name": "Kernel",
            "ecosystem": "Linux"
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            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90149.json"
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      ],
      "modified": "2026-11-01T02:31:02.246874798Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/163c16e01f53fc8eb8d0f3484ae6c382265ecbbd",
        "https://git.kernel.org/stable/c/2b03ebbf8d5e8f6af4ecd6c65375232dd1ec32cc",
        "https://git.kernel.org/stable/c/336b6da10021c69a8f273bbacdf7432fdc89a06f",
        "https://git.kernel.org/stable/c/436a214514e24103159aea455147d58b44a8a585",
        "https://git.kernel.org/stable/c/5527af72b0100c94287bfec901b6313eeac567ca",
        "https://git.kernel.org/stable/c/e55d7fec8a9290f73032ee34c35dd68532809633",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90149.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-90149",
        "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/2026/90xxx/CVE-2026-90149.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-90149",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489733,
  "published_at": "2026-09-17T16:06:43.671+00:00"
}