CVE-2026-90039 (GCVE-0-2026-90039)
Vulnerability from cvelistv5
Published
2026-09-16 10:33
Modified
2026-10-19 08:56
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: NFSD: Guard admin state-revocation walks with NFSD_NET_UP Writing to /proc/fs/nfsd/unlock_filesystem, or sending the NFSD_CMD_UNLOCK_FILESYSTEM or NFSD_CMD_UNLOCK_EXPORT netlink command, walks the NFSv4 client hash tables to revoke open state and cancel async COPY operations. All three handlers gate that walk on nn->nfsd_serv, but a listener added via portlist or netlink listener_set sets nn->nfsd_serv before any nfsd thread starts. nfsd_startup_net() has not yet allocated nn->conf_id_hashtbl, so the walkers dereference a NULL table. A local administrator with CAP_SYS_ADMIN can crash the kernel this way without ever starting the server. nn->nfsd_serv is set when the service is created, which precedes table allocation. NFSD_NET_UP instead brackets the window where the tables are live: set at the end of nfsd_startup_net() and cleared in nfsd_shutdown_net() after they are freed, both under nfsd_mutex. Gating the three unlock paths on NFSD_NET_UP fixes the startup-time NULL dereference while preserving the earlier post-shutdown use-after-free fix.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1ac3629bf012592cb0320e52a1cceb319a05ad17
Version: 1ac3629bf012592cb0320e52a1cceb319a05ad17
Version: 1ac3629bf012592cb0320e52a1cceb319a05ad17
Version: 1ac3629bf012592cb0320e52a1cceb319a05ad17
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c",
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          "vendor": "Linux",
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      "cpeApplicability": [
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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\nNFSD: Guard admin state-revocation walks with NFSD_NET_UP\n\nWriting to /proc/fs/nfsd/unlock_filesystem, or sending the\nNFSD_CMD_UNLOCK_FILESYSTEM or NFSD_CMD_UNLOCK_EXPORT netlink command,\nwalks the NFSv4 client hash tables to revoke open state and cancel\nasync COPY operations.  All three handlers gate that walk on\nnn-\u003enfsd_serv, but a listener added via portlist or netlink\nlistener_set sets nn-\u003enfsd_serv before any nfsd thread starts.\nnfsd_startup_net() has not yet allocated nn-\u003econf_id_hashtbl, so the\nwalkers dereference a NULL table.  A local administrator with\nCAP_SYS_ADMIN can crash the kernel this way without ever starting the\nserver.\n\nnn-\u003enfsd_serv is set when the service is created, which precedes\ntable allocation.  NFSD_NET_UP instead brackets the window where the\ntables are live: set at the end of nfsd_startup_net() and cleared in\nnfsd_shutdown_net() after they are freed, both under nfsd_mutex.\nGating the three unlock paths on NFSD_NET_UP fixes the startup-time\nNULL dereference while preserving the earlier post-shutdown\nuse-after-free fix."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:56:56.714Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/73bf459d696ecf207a9037bf9bb70c51a459469e"
        },
        {
          "url": "https://git.kernel.org/stable/c/104a51265042b4424085741c963cb858ac29ec0b"
        },
        {
          "url": "https://git.kernel.org/stable/c/0146467a2fce845cb6629979c3e9c58dd3d3a6a3"
        },
        {
          "url": "https://git.kernel.org/stable/c/2f3e6638aebc0ab8afb8b4e9816ea9a1cad85378"
        }
      ],
      "title": "NFSD: Guard admin state-revocation walks with NFSD_NET_UP",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90039",
    "datePublished": "2026-09-16T10:33:38.091Z",
    "dateReserved": "2026-09-11T19:38:34.783Z",
    "dateUpdated": "2026-10-19T08:56:56.714Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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