userfaultfd: prevent registration of special VMAs
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.
CVE-2026-68166
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:CVE-2026-68166
Kernel
Source reference: /affected/1/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 6.6.153
Source reference:
/affected/1/ranges6.12.105Source reference:
/affected/1/ranges6.18.44Source reference:
/affected/1/ranges7.1.6Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"type": "GIT",
"events": [
{
"introduced": "54007f818206dc27309ca423df4c87dd160a7208"
},
{
"fixed": "d974b4b786214883bd8e56bda10b454c80fd6205"
},
{
"fixed": "495a28d5a100be1b232633f4c2dcc42ba10b3796"
},
{
"fixed": "165613191ad9d034bf17c00e3a142f9561597ec5"
},
{
"fixed": "0c26202b157f1efc3cd2f26f5c30f59b508a6a5d"
},
{
"fixed": "3c58f641e813c3c71039f8fd4d4e2a3aab713288"
}
]
}
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68166.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.6.0"
},
{
"fixed": "6.6.153"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.7.0"
},
{
"fixed": "6.12.105"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.13.0"
},
{
"fixed": "6.18.44"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.19.0"
},
{
"fixed": "7.1.6"
}
]
}
],
"package": {
"name": "Kernel",
"ecosystem": "Linux"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68166.json"
}
}
]- Related CVEs
- CVE-2026-68166
Source reference:
/id
Publisher severity
No explicit severity was provided.
- Event
- #50761 · Revision 1
- Added to Heist Feed
- Publisher date