CVE-2026-68166

Name	CVE-2026-68166
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DSA-6466-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
linux (PTS)	bullseye	5.10.223-1	fixed
	bullseye (security)	5.10.262-1	fixed
	bookworm	6.1.176-1	fixed
	bookworm (security)	6.1.180-1	fixed
	trixie	6.12.94-1	vulnerable
	trixie (security)	6.12.107-1	fixed
	forky	7.1.8-2	fixed
	sid	7.1.12-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Origin
linux	source	bullseye	(not affected)
linux	source	bookworm	(not affected)
linux	source	trixie	6.12.105-1	DSA-6466-1
linux	source	(unstable)	7.1.6-1

Notes

[bookworm] - linux <not-affected> (Vulnerable code not present)
[bullseye] - linux <not-affected> (Vulnerable code not present)
https://git.kernel.org/linus/3c58f641e813c3c71039f8fd4d4e2a3aab713288 (7.2-rc5)