Skip to content
Fencer Vulns
no cvss —

CVE-2026-68166 json

userfaultfd: prevent registration of special VMAs

published 2026-08-10 2 mo ago modified 2026-11-06 2 d ago also EUVD-2026-55552

cvss
—
not scored
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 10%
public exploits
0
none known

Summary

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.

Patch / fix

  • Linux Linux 6.6.153, 6.12.105, 6.18.44, 7.1.6, 7.2
  • linux Debian 13 6.12.105-1
  • linux Debian 14 7.1.6-1
  • linux-6.12 Debian 12 6.12.107-1~deb12u1

debian advisories DEBIAN-CVE-2026-68166

  • linux Ubuntu 26.04 LTS 7.0.0-38.38
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1014.14
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1014.14
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1008.9
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1015.15
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1017.17
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-38.38.1
  • linux-oracle Ubuntu 26.04 LTS 7.0.0-1013.13

ubuntu advisories UBUNTU-CVE-2026-68166

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 9 5.14.0-687.44.1.el9_8
  • rv RHEL 9 5.14.0-687.44.1.el9_8
  • perf RHEL 9 5.14.0-687.44.1.el9_8
  • rtla RHEL 9 5.14.0-687.44.1.el9_8
  • libperf RHEL 9 5.14.0-687.44.1.el9_8
  • kernel-rt RHEL 9 5.14.0-687.44.1.el9_8
  • kernel-64k RHEL 9 5.14.0-687.44.1.el9_8
  • kernel-core RHEL 9 5.14.0-687.44.1.el9_8

red hat advisories RHSA-2026:69089RHSA-2026:67720RHSA-2026:63129RHSA-2026:61887

  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.81.1
  • kernel-source SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-default SLE Workstation Extension 15 SP7, SLE Module for Legacy 15 SP7, SLE Module for Basesystem 15 SP7 +2 more 6.4.0-150700.53.81.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1
  • kernel-obs-build SLE Module for Development Tools 15 SP7 6.4.0-150700.53.81.1
  • kernel-default-base SLE Module for Basesystem 15 SP7 6.4.0-150700.53.81.1.150700.17.45.1

suse advisories SUSE-SU-2026:4254-1SUSE-SU-2026:23887-1SUSE-SU-2026:23902-1SUSE-SU-2026:23897-1SUSE-SU-2026:23881-1SUSE-SU-2026:4120-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.38.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.38.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.38.1

opensuse advisories openSUSE-SU-2026:21910-1

  • kernel AlmaLinux 9 5.14.0-687.44.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.44.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.44.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.44.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.44.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.44.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.44.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.44.1.el9_8

almalinux advisories ALSA-2026:63129ALSA-2026:61887

  • kernel Rocky Linux 9 5.14.0-687.44.1.el9_8
  • kernel Rocky Linux 10 6.12.0-211.50.1.el10_2

rocky linux advisories RLSA-2026:63129RLSA-2026:61887

  • kernel Azure Linux 3.0 6.6.157.1-1

azure linux advisories AZL-94734

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-68166 updated cvss 7.3

kernel: Linux kernel: Arbitrary code execution via userfaultfd shadow stack manipulation

  • Red Hat CodeReady Linux Builder EUS (v.9.6) libperf 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-s390x 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-x86_64 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-aarch64 5.14.0-570.141.1.el9_6, kernel-debuginfo-common-ppc64le 5.14.0-570.141.1.el9_6
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.44.1.el9_8, perf 5.14.0-687.44.1.el9_8, rtla 5.14.0-687.44.1.el9_8, python3-perf 5.14.0-687.44.1.el9_8, kernel-devel-matched 5.14.0-687.44.1.el9_8, kernel-64k-devel-matched 5.14.0-687.44.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.50.1.el10_2, perf 6.12.0-211.50.1.el10_2, rtla 6.12.0-211.50.1.el10_2, python3-perf 6.12.0-211.50.1.el10_2, kernel-devel-matched 6.12.0-211.50.1.el10_2, kernel-64k-devel-matched 6.12.0-211.50.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) rv 6.12.0-55.105.1.el10_0, perf 6.12.0-55.105.1.el10_0, rtla 6.12.0-55.105.1.el10_0, python3-perf 6.12.0-55.105.1.el10_0, kernel-devel-matched 6.12.0-55.105.1.el10_0, kernel-64k-devel-matched 6.12.0-55.105.1.el10_0, +7 more
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) rv 5.14.0-570.141.1.el9_6, perf 5.14.0-570.141.1.el9_6, rtla 5.14.0-570.141.1.el9_6, python3-perf 5.14.0-570.141.1.el9_6, kernel-devel-matched 5.14.0-570.141.1.el9_6, kernel-64k-devel-matched 5.14.0-570.141.1.el9_6, +7 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.44.1.el9_8, kernel-64k 5.14.0-687.44.1.el9_8, kernel-core 5.14.0-687.44.1.el9_8, kernel-tools 5.14.0-687.44.1.el9_8, kernel-modules 5.14.0-687.44.1.el9_8, kernel-64k-core 5.14.0-687.44.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.50.1.el10_2, kernel-64k 6.12.0-211.50.1.el10_2, kernel-core 6.12.0-211.50.1.el10_2, kernel-tools 6.12.0-211.50.1.el10_2, kernel-modules 6.12.0-211.50.1.el10_2, kernel-64k-core 6.12.0-211.50.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel 6.12.0-55.105.1.el10_0, kernel-64k 6.12.0-55.105.1.el10_0, kernel-core 6.12.0-55.105.1.el10_0, kernel-tools 6.12.0-55.105.1.el10_0, kernel-modules 6.12.0-55.105.1.el10_0, kernel-64k-core 6.12.0-55.105.1.el10_0, +27 more
    fixed: vendor fix RHSA-2026:69089
show 13 more
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel 5.14.0-570.141.1.el9_6, kernel-64k 5.14.0-570.141.1.el9_6, kernel-core 5.14.0-570.141.1.el9_6, kernel-tools 5.14.0-570.141.1.el9_6, kernel-modules 5.14.0-570.141.1.el9_6, kernel-64k-core 5.14.0-570.141.1.el9_6, +27 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.44.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.44.1.el9_8
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.50.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.50.1.el10_2
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) libperf 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-s390x 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-x86_64 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-aarch64 6.12.0-55.105.1.el10_0, kernel-debuginfo-common-ppc64le 6.12.0-55.105.1.el10_0
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.44.1.el9_8, kernel-rt-64k 5.14.0-687.44.1.el9_8, kernel-rt-core 5.14.0-687.44.1.el9_8, kernel-rt-modules 5.14.0-687.44.1.el9_8, kernel-rt-64k-core 5.14.0-687.44.1.el9_8, kernel-rt-debug-core 5.14.0-687.44.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-64k 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-64k-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt 6.12.0-55.105.1.el10_0, kernel-rt-64k 6.12.0-55.105.1.el10_0, kernel-rt-core 6.12.0-55.105.1.el10_0, kernel-rt-modules 6.12.0-55.105.1.el10_0, kernel-rt-64k-core 6.12.0-55.105.1.el10_0, kernel-rt-debug-core 6.12.0-55.105.1.el10_0, +14 more
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt 5.14.0-570.141.1.el9_6, kernel-rt-64k 5.14.0-570.141.1.el9_6, kernel-rt-core 5.14.0-570.141.1.el9_6, kernel-rt-modules 5.14.0-570.141.1.el9_6, kernel-rt-64k-core 5.14.0-570.141.1.el9_6, kernel-rt-debug-core 5.14.0-570.141.1.el9_6, +14 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.44.1.el9_8, kernel-rt-core 5.14.0-687.44.1.el9_8, kernel-rt-modules 5.14.0-687.44.1.el9_8, kernel-rt-debug-core 5.14.0-687.44.1.el9_8, kernel-rt-modules-core 5.14.0-687.44.1.el9_8, kernel-rt-debug-modules 5.14.0-687.44.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:63129
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.50.1.el10_2, kernel-rt-core 6.12.0-211.50.1.el10_2, kernel-rt-modules 6.12.0-211.50.1.el10_2, kernel-rt-debug-core 6.12.0-211.50.1.el10_2, kernel-rt-modules-core 6.12.0-211.50.1.el10_2, kernel-rt-debug-modules 6.12.0-211.50.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:61887
  • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt 6.12.0-55.105.1.el10_0, kernel-rt-kvm 6.12.0-55.105.1.el10_0, kernel-rt-core 6.12.0-55.105.1.el10_0, kernel-rt-modules 6.12.0-55.105.1.el10_0, kernel-rt-debug-kvm 6.12.0-55.105.1.el10_0, kernel-rt-debug-core 6.12.0-55.105.1.el10_0, +6 more
    fixed: vendor fix RHSA-2026:69089
  • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt 5.14.0-570.141.1.el9_6, kernel-rt-kvm 5.14.0-570.141.1.el9_6, kernel-rt-core 5.14.0-570.141.1.el9_6, kernel-rt-modules 5.14.0-570.141.1.el9_6, kernel-rt-debug-kvm 5.14.0-570.141.1.el9_6, kernel-rt-debug-core 5.14.0-570.141.1.el9_6, +6 more
    fixed: vendor fix RHSA-2026:67720
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more Red Hat Enterprise Linux for NVIDIA 26 kernel
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
2 d ago

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-08).

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.