{"api_version":"1","generated_at":"2026-08-22T09:26:13+00:00","cve":"CVE-2026-68166","urls":{"html":"https://cve.report/CVE-2026-68166","api":"https://cve.report/api/cve/CVE-2026-68166.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-68166","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-68166"},"summary":{"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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-10 13:20:03","updated_at":"2026-08-17 05:18:17"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288","name":"https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","name":"https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5","name":"https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-68166","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-68166","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 54007f818206dc27309ca423df4c87dd160a7208 165613191ad9d034bf17c00e3a142f9561597ec5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 54007f818206dc27309ca423df4c87dd160a7208 0c26202b157f1efc3cd2f26f5c30f59b508a6a5d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 54007f818206dc27309ca423df4c87dd160a7208 3c58f641e813c3c71039f8fd4d4e2a3aab713288 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.6","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.44 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.6 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"68166","cve":"CVE-2026-68166","epss":"0.001980000","percentile":"0.099080000","score_date":"2026-08-17","updated_at":"2026-08-18 00:11:47"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["mm/userfaultfd.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"165613191ad9d034bf17c00e3a142f9561597ec5","status":"affected","version":"54007f818206dc27309ca423df4c87dd160a7208","versionType":"git"},{"lessThan":"0c26202b157f1efc3cd2f26f5c30f59b508a6a5d","status":"affected","version":"54007f818206dc27309ca423df4c87dd160a7208","versionType":"git"},{"lessThan":"3c58f641e813c3c71039f8fd4d4e2a3aab713288","status":"affected","version":"54007f818206dc27309ca423df4c87dd160a7208","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["mm/userfaultfd.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.6"},{"lessThan":"6.6","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.44","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.6","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.44","versionStartIncluding":"6.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.6","versionStartIncluding":"6.6","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2","versionStartIncluding":"6.6","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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."}],"providerMetadata":{"dateUpdated":"2026-08-17T05:00:06.489Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/165613191ad9d034bf17c00e3a142f9561597ec5"},{"url":"https://git.kernel.org/stable/c/0c26202b157f1efc3cd2f26f5c30f59b508a6a5d"},{"url":"https://git.kernel.org/stable/c/3c58f641e813c3c71039f8fd4d4e2a3aab713288"}],"title":"userfaultfd: prevent registration of special VMAs","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-68166","datePublished":"2026-08-10T11:59:34.576Z","dateReserved":"2026-07-30T09:28:09.372Z","dateUpdated":"2026-08-17T05:00:06.489Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-10 13:20:03","lastModifiedDate":"2026-08-17 05:18:17","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"68166","Ordinal":"1","Title":"userfaultfd: prevent registration of special VMAs","CVE":"CVE-2026-68166","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"68166","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"userfaultfd: prevent registration of special VMAs"}]}}}