{"id":"CVE-2026-68166","title":"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","summary":"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 regis…","severity":"high","published":"2026-08-10","updated":"2026-08-23","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-68166","references":[{"url":"https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/495a28d5a100be1b232633f4c2dcc42ba10b3796","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d974b4b786214883bd8e56bda10b454c80fd6205","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-68166.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-68166"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2513167"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-68166"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68166"},{"url":"https://access.redhat.com/errata/RHSA-2026:61887"},{"url":"https://access.redhat.com/errata/RHSA-2026:67720"},{"url":"https://access.redhat.com/errata/RHSA-2026:63129"},{"url":"https://access.redhat.com/errata/RHSA-2026:69089"}],"tags":["nvd","csaf","vex","red-hat"],"epss":0.002,"epssPercentile":0.10164,"ingestedAt":"2026-08-23T13:48:06.487Z","vendor":"Red Hat","product":"Red Hat Enterprise Linux BaseOS (v. 10)","affected":["enterprise_linux_appstream_v_10","enterprise_linux_appstream_eus_v_9_6","enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_10","enterprise_linux_baseos_eus_v_9_6","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_10","codeready_linux_builder_eus_v_9_6","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_real_time_for_nfv_eus_v_9_6","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_10","enterprise_linux_real_time_eus_v_9_6","enterprise_linux_real_time_v_9"],"patched":["enterprise_linux_appstream_v_10","enterprise_linux_appstream_eus_v_9_6","enterprise_linux_appstream_v_9","enterprise_linux_baseos_v_10","enterprise_linux_baseos_eus_v_9_6","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_v_10","codeready_linux_builder_eus_v_9_6","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_real_time_for_nfv_eus_v_9_6","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_v_10","enterprise_linux_real_time_eus_v_9_6","enterprise_linux_real_time_v_9"],"cvss":7.3,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H","cvssSource":"vendor","cwe":["CWE-94"],"slug":"CVE-2026-68166","body":"## Overview\n\nIn 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't 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:61887** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-09-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:61887)\n- **RHSA-2026:67720** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6), Red Hat Enterprise Linux Real Time EUS (v.9.6) · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67720)\n- **RHSA-2026:63129** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-09-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:63129)\n- **RHSA-2026:69089** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0) · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69089)","depth":"twilight","depthScore":40,"depthScoreParts":{"impact":40.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":205498,"id":"CVE-2026-68166","ts":1789576722105,"field":"cvss","old":null,"new":"7.3"},{"seq":205497,"id":"CVE-2026-68166","ts":1789576722105,"field":"severity","old":"none","new":"high"}]}