memfd: deny writeable mappings when implying SEAL_WRITE

{
  "id": "5d902eb2a1ef0ece780ed131f04ab7a75be395cda61c58b56cdbdbd8e34b4e80",
  "url": "https://osv.dev/vulnerability/CVE-2026-63952",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "memfd: deny writeable mappings when implying SEAL_WRITE",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: memfd: deny writeable mappings when implying SEAL_WRITE When SEAL_EXEC is added, SEAL_WRITE is implied to make W^X. But the implied seal is set after the check that makes sure the memfd can not have any writable mappings. This means one can use SEAL_EXEC to apply SEAL_WRITE while having writeable mappings. This breaks the contract that SEAL_WRITE provides and can be used by an attacker to pass a memfd that appears to be write sealed but can still be modified arbitrarily. Fix this by adding the implied seals before the call for mapping_deny_writable() is done.",
    "evidence": "osv:CVE-2026-63952",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.143",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.93",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.35",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.0.12",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-63952",
      "aliases": [
        "CVE-2026-63952"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
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              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "b3f4f82d1315f1439059a83d1c22c51a5b43d99e"
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                {
                  "fixed": "3be2a24f7f72ad7321ed6ad1715b956a4527bcf4"
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                {
                  "fixed": "0995d1f79aed8ccbf62056189dd53fd19726ea08"
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                {
                  "fixed": "555702282d4536a865dfffb1cd4f6028f196e7e8"
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                {
                  "fixed": "3b041514cb6eae45869b020f743c14d983363222"
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              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63952.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.3.0"
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                {
                  "fixed": "6.6.143"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.7.0"
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                  "introduced": "6.13.0"
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                  "fixed": "6.18.35"
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            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-63952.json"
          }
        }
      ],
      "modified": "2026-10-30T02:30:56.873672797Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0995d1f79aed8ccbf62056189dd53fd19726ea08",
        "https://git.kernel.org/stable/c/3b041514cb6eae45869b020f743c14d983363222",
        "https://git.kernel.org/stable/c/3be2a24f7f72ad7321ed6ad1715b956a4527bcf4",
        "https://git.kernel.org/stable/c/555702282d4536a865dfffb1cd4f6028f196e7e8",
        "https://git.kernel.org/stable/c/b3f4f82d1315f1439059a83d1c22c51a5b43d99e",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63952.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-63952",
        "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/2026/63xxx/CVE-2026-63952.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-63952",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517078,
  "published_at": "2026-07-19T14:55:44.809+00:00"
}