CVE-2025-40212 (GCVE-0-2025-40212)

Vulnerability from cvelistv5 – Published: 2025-11-24 13:04 – Updated: 2025-12-01 06:20
VLAI?
Title
nfsd: fix refcount leak in nfsd_set_fh_dentry()
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix refcount leak in nfsd_set_fh_dentry() nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find the various exported filesystems using LOOKUP requests from a known root filehandle. NFSv3 uses the MOUNT protocol to find those exported filesystems and so is not given access to the pseudo root filesystem. If a v3 (or v2) client uses a filehandle from that filesystem, nfsd_set_fh_dentry() will report an error, but still stores the export in "struct svc_fh" even though it also drops the reference (exp_put()). This means that when fh_put() is called an extra reference will be dropped which can lead to use-after-free and possible denial of service. Normal NFS usage will not provide a pseudo-root filehandle to a v3 client. This bug can only be triggered by the client synthesising an incorrect filehandle. To fix this we move the assignments to the svc_fh later, after all possible error cases have been detected.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 , < b6bc86ce3944b10b9fc181fc00c1a520a20ed965 (git)
Affected: ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 , < c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2 (git)
Affected: ef7f6c4904d03ccd7478e1ac20ed75f79c4ac444 , < 8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c (git)
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    Linux Linux Affected: 6.12
Unaffected: 0 , < 6.12 (semver)
Unaffected: 6.12.59 , ≤ 6.12.* (semver)
Unaffected: 6.17.9 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfsfh.c"
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix refcount leak in nfsd_set_fh_dentry()\n\nnfsd exports a \"pseudo root filesystem\" which is used by NFSv4 to find\nthe various exported filesystems using LOOKUP requests from a known root\nfilehandle.  NFSv3 uses the MOUNT protocol to find those exported\nfilesystems and so is not given access to the pseudo root filesystem.\n\nIf a v3 (or v2) client uses a filehandle from that filesystem,\nnfsd_set_fh_dentry() will report an error, but still stores the export\nin \"struct svc_fh\" even though it also drops the reference (exp_put()).\nThis means that when fh_put() is called an extra reference will be dropped\nwhich can lead to use-after-free and possible denial of service.\n\nNormal NFS usage will not provide a pseudo-root filehandle to a v3\nclient.  This bug can only be triggered by the client synthesising an\nincorrect filehandle.\n\nTo fix this we move the assignments to the svc_fh later, after all\npossible error cases have been detected."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-01T06:20:17.962Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/b6bc86ce3944b10b9fc181fc00c1a520a20ed965"
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        {
          "url": "https://git.kernel.org/stable/c/8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c"
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      ],
      "title": "nfsd: fix refcount leak in nfsd_set_fh_dentry()",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40212",
    "datePublished": "2025-11-24T13:04:20.888Z",
    "dateReserved": "2025-04-16T07:20:57.179Z",
    "dateUpdated": "2025-12-01T06:20:17.962Z",
    "state": "PUBLISHED"
  },
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  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40212\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-11-24T13:16:02.813\",\"lastModified\":\"2025-11-25T22:16:16.690\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnfsd: fix refcount leak in nfsd_set_fh_dentry()\\n\\nnfsd exports a \\\"pseudo root filesystem\\\" which is used by NFSv4 to find\\nthe various exported filesystems using LOOKUP requests from a known root\\nfilehandle.  NFSv3 uses the MOUNT protocol to find those exported\\nfilesystems and so is not given access to the pseudo root filesystem.\\n\\nIf a v3 (or v2) client uses a filehandle from that filesystem,\\nnfsd_set_fh_dentry() will report an error, but still stores the export\\nin \\\"struct svc_fh\\\" even though it also drops the reference (exp_put()).\\nThis means that when fh_put() is called an extra reference will be dropped\\nwhich can lead to use-after-free and possible denial of service.\\n\\nNormal NFS usage will not provide a pseudo-root filehandle to a v3\\nclient.  This bug can only be triggered by the client synthesising an\\nincorrect filehandle.\\n\\nTo fix this we move the assignments to the svc_fh later, after all\\npossible error cases have been detected.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/8a7348a9ed70bda1c1f51d3f1815bcbdf9f3b38c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b6bc86ce3944b10b9fc181fc00c1a520a20ed965\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c83d7365cec5eb5ebeeee2a72e29b4ca58a7e4c2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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