GHSA-HV63-47WX-6P3X

Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-10 15:33
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

userfaultfd: prevent registration of special VMAs

Vova Tokarev says:

userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY.

Update vma_can_userfault() to reject VM_SHADOW_STACK.

While on it, also reject VM_SPECIAL so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd.

Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-68166"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-10T13:20:03Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nuserfaultfd: prevent registration of special VMAs\n\nVova Tokarev says:\n\n  userfaultfd allows registration on shadow stack VMAs.  With userfaultfd\n  access, you can register on the shadow stack, discard a page ... and\n  inject a page with chosen return addresses via UFFDIO_COPY.\n\nUpdate vma_can_userfault() to reject VM_SHADOW_STACK.\n\nWhile on it, also reject VM_SPECIAL so that if a driver would implement\nvm_uffd_ops, it wouldn\u0027t be possible to register special VMAs with\nuserfaultfd.\n\nSince VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude\nhugetlb VMAs from the check for VM_SPECIAL.",
  "id": "GHSA-hv63-47wx-6p3x",
  "modified": "2026-08-10T15:33:39Z",
  "published": "2026-08-10T15:33:38Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68166"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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