{"id":"CVE-2026-68166","state":"PUBLISHED","title":"userfaultfd: prevent registration of special VMAs","description":"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 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.","publishedAt":"2026-08-10T11:59:34.576Z","updatedAt":"2026-08-23T12:46:02.309Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"d974b4b786214883bd8e56bda10b454c80fd6205","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"495a28d5a100be1b232633f4c2dcc42ba10b3796","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"165613191ad9d034bf17c00e3a142f9561597ec5","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"3c58f641e813c3c71039f8fd4d4e2a3aab713288","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/userfaultfd.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"6.6.153","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.105","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.44","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/userfaultfd.c"]}],"references":["https://git.kernel.org/stable/c/d974b4b786214883bd8e56bda10b454c80fd6205","https://git.kernel.org/stable/c/495a28d5a100be1b232633f4c2dcc42ba10b3796","https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5","https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/68xxx/CVE-2026-68166.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68166","state":"PUBLISHED","datePublished":"2026-08-10T11:59:34.576Z","dateUpdated":"2026-08-23T12:46:02.309Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-30T09:28:09.372Z"},"containers":{"cna":{"title":"userfaultfd: prevent registration of special VMAs","descriptions":[{"lang":"en","value":"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 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"d974b4b786214883bd8e56bda10b454c80fd6205","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"495a28d5a100be1b232633f4c2dcc42ba10b3796","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"165613191ad9d034bf17c00e3a142f9561597ec5","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","versionType":"git"},{"version":"54007f818206dc27309ca423df4c87dd160a7208","status":"affected","lessThan":"3c58f641e813c3c71039f8fd4d4e2a3aab713288","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/userfaultfd.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.6","versionType":"semver"},{"version":"6.6.153","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.105","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.44","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/userfaultfd.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/d974b4b786214883bd8e56bda10b454c80fd6205"},{"url":"https://git.kernel.org/stable/c/495a28d5a100be1b232633f4c2dcc42ba10b3796"},{"url":"https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5"},{"url":"https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d"},{"url":"https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-23T12:46:02.309Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.6.153"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.12.105"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"6.18.44"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}