GHSA-HV63-47WX-6P3X
Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-23 15:32In 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.
{
"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": "2026-08-23T15:32:56Z",
"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"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/495a28d5a100be1b232633f4c2dcc42ba10b3796"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d974b4b786214883bd8e56bda10b454c80fd6205"
}
],
"schema_version": "1.4.0",
"severity": []
}
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