userfaultfd: prevent registration of special VMAs

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Summary

CVECVE-2026-68166
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-10 13:20:03 UTC
Updated2026-08-17 05:18:17 UTC
DescriptionIn 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.

Risk And Classification

EPSS: 0.001980000 probability, percentile 0.099080000 (date 2026-08-17)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 54007f818206dc27309ca423df4c87dd160a7208 165613191ad9d034bf17c00e3a142f9561597ec5 git Not specified
CNA Linux Linux affected 54007f818206dc27309ca423df4c87dd160a7208 0c26202b157f1efc3cd2f26f5c30f59b508a6a5d git Not specified
CNA Linux Linux affected 54007f818206dc27309ca423df4c87dd160a7208 3c58f641e813c3c71039f8fd4d4e2a3aab713288 git Not specified
CNA Linux Linux affected 6.6 Not specified
CNA Linux Linux unaffected 6.6 semver Not specified
CNA Linux Linux unaffected 6.18.44 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.6 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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