{"schema":"threatline.record/2","record":{"id":"CVE-2026-98717","aliases":[],"summary":"KVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86/mmu: Bail from shadow walks if the root is invalid or a dummy\n\nWhen walking shadow page tables, immediately terminate the walk if the root\nis a \"dummy\" root, i.e. a root whose top-level page table is backed by the\nzero page, but otherwise doesn't exist.  If memslot creation races with a\nstage-2 page fault (EPT violation or #NPF) from L2, then if the stars align,\nKVM will attempt to walk shadow page tables using the zero page and hit a\nNULL pointer deref.\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000021\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 0 P4D 0\n  Oops: Oops: 0000 [#1] SMP\n  CPU: 30 UID: 1000 PID: 941 Comm: qemu Not tainted 7.2.0-rc2-1b731e5ded48-next-vm #1741 PREEMPTLAZY\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  RIP: 0010:__kvm_mmu_invalidate_addr+0xea/0x210 [kvm]\n  Call Trace:\n   <TASK>\n   kvm_mmu_invalidate_addr+0x92/0xe0 [kvm]\n   __kvm_inject_emulated_page_fault+0x67/0x80 [kvm]\n   ept_page_fault+0x160/0x850 [kvm]\n   kvm_mmu_do_page_fault+0x102/0x1f0 [kvm]\n   kvm_mmu_page_fault+0x8e/0x6b0 [kvm]\n   vmx_handle_exit+0x163/0x640 [kvm_intel]\n   kvm_arch_vcpu_ioctl_run+0x960/0x2120 [kvm]\n   kvm_vcpu_ioctl+0x2c7/0x970 [kvm]\n   __x64_sys_ioctl+0x90/0xd0\n   do_syscall_64+0x67/0x5f0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x7f606d0b53bb\n\nOpportunistically harden the shadow walks against fully invalid roots, but\nWARN, as all callers are expected/required to pre-check for a valid root.\nDon't WARN in the dummy root case as the whole point of using a dummy root\nis to provide a root that's valid enough to enter the guest, i.e. it should\nJust Work for all flows except those that *need* to know about dummy roots.\n\nAlternatively, KVM could allocate a dedicated page and associated shadow\npage structure for the dummy root, which is very tempting as it such an\napproach should be more resilient against unexpected behavior.  But that\nwould be a much larger and thus riskier change than simply terminating\nwalks of dummy roots.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98717","source_modified_at":"2026-10-21T12:56:02.536Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"0e3223d8d00ac05849661f1b8b476d3caca251cf","lessThan":"951fce1510645ba5df38da6fb85ece5726ec347d","status":"affected","versionType":"git"},{"version":"0e3223d8d00ac05849661f1b8b476d3caca251cf","lessThan":"e1bcabc07efd029ab414894127411129ffdb8b48","status":"affected","versionType":"git"},{"version":"0e3223d8d00ac05849661f1b8b476d3caca251cf","lessThan":"97c1dcce17ef27853860c781f9912257e6adbf7c","status":"affected","versionType":"git"},{"version":"0e3223d8d00ac05849661f1b8b476d3caca251cf","lessThan":"681e31f03ec9219099a66a0f6e1bc48e1b5aa914","status":"affected","versionType":"git"},{"version":"0e3223d8d00ac05849661f1b8b476d3caca251cf","lessThan":"b6249c1d5665098c8bf12f8d3e4712bf04c775bc","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98717","source_modified_at":"2026-10-21T12:56:02.536Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"6.6","status":"affected"},{"version":"0","lessThan":"6.6","status":"unaffected","versionType":"semver"},{"version":"6.6.160","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.113","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.56","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.10","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98717","source_modified_at":"2026-10-21T12:56:02.536Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"951fce1510645ba5df38da6fb85ece5726ec347d","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98717","source_modified_at":"2026-10-21T12:56:02.536Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"97c1dcce17ef27853860c781f9912257e6adbf7c","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98717","source_modified_at":"2026-10-21T12:56:02.536Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"681e31f03ec9219099a66a0f6e1bc48e1b5aa914","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.002,"percentile":0.09313,"score_date":"2026-10-23"},"published_at":"2026-10-18T15:46:51.862Z","modified_at":"2026-10-21T12:56:02.536Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98717","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-21T12:56:02.536Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98717","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/951fce1510645ba5df38da6fb85ece5726ec347d"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/e1bcabc07efd029ab414894127411129ffdb8b48"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/97c1dcce17ef27853860c781f9912257e6adbf7c"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/681e31f03ec9219099a66a0f6e1bc48e1b5aa914"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/b6249c1d5665098c8bf12f8d3e4712bf04c775bc"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-21T12:56:02.536Z","content_hash":"4d0c7cb35ffefa1cfd9c28db183ff66a54861ea5b99f234b0448d67994c3e6d0"}}