{"schema":"threatline.record/2","record":{"id":"CVE-2026-99176","aliases":[],"summary":"KVM: nVMX: Reset MMU back to the root MMU if loading L2 state fails for !VM-Entry","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: nVMX: Reset MMU back to the root MMU if loading L2 state fails for !VM-Entry\n\nReset the vCPU's MMU pointer back to the root MMU if loading L2 state fails\nin the \"not from VM-Entry\" case, i.e. when emulating RSM or handling\nKVM_SET_NESTED_STATE.  Failure to unwind the MMU pointer results in KVM\ntrying to run L1 with a nested MMU, and is especially problematic if the\nvCPU manages to free its nested state before the VM crashes.  Constructing\nthe root for a nested EPT MMU goes through vmcs12, which is dynamically\nallocated/freed when nVMX is enabled/disabled.  And so if the nested state\nis freed with the MMU still pointing at the nested MMU, KVM will hit a NULL\npointer deref when attempting to get L1=>L2 EPTP.\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000078\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 114a2d067 P4D 111743067 PUD 11141f067 PMD 0\n  Oops: Oops: 0000 [#1] SMP\n  CPU: 20 UID: 1000 PID: 1272 Comm: nested_tdp_faul Not tainted 7.3.0-rc4-8c89f11d1a99b-sink-vm #1914 PREEMPTLAZY\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  RIP: 0010:nested_ept_get_eptp+0xb/0x10 [kvm_intel]\n  Call Trace:\n   <TASK>\n   kvm_mmu_load+0xcd/0x870 [kvm]\n   kvm_arch_vcpu_ioctl_run+0x18f5/0x1f80 [kvm]\n   kvm_vcpu_ioctl+0x2c7/0x970 [kvm]\n   __x64_sys_ioctl+0x90/0xd0\n   do_syscall_64+0x9c/0x4d0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x47491b\n   </TASK>\n  Modules linked in: kvm_intel kvm irqbypass\n  CR2: 0000000000000078\n  ---[ end trace 0000000000000000 ]---\n  RIP: 0010:nested_ept_get_eptp+0xb/0x10 [kvm_intel]\n\n[sean: write changelog]","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99176","source_modified_at":"2026-10-28T10:35:30.615Z","fetched_at":"2026-10-28T15:55:58.673066Z","product":"Linux","vendor":"Linux","versions":[{"version":"72e9cbdb43384ceacc49e2fb6b8c8fb7c5988778","lessThan":"d00d5f534a8238674755e59826a6c7d3c8efb870","status":"affected","versionType":"git"},{"version":"72e9cbdb43384ceacc49e2fb6b8c8fb7c5988778","lessThan":"c9716f956216eb74ab0aad7f633586edd49e0322","status":"affected","versionType":"git"},{"version":"72e9cbdb43384ceacc49e2fb6b8c8fb7c5988778","lessThan":"c8f4cfe1cf93bce924e27f2abead7a4c4a487505","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-99176","source_modified_at":"2026-10-28T10:35:30.615Z","fetched_at":"2026-10-28T15:55:58.673066Z","product":"Linux","vendor":"Linux","versions":[{"version":"4.15","status":"affected"},{"version":"0","lessThan":"4.15","status":"unaffected","versionType":"semver"},{"version":"6.18.59","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.13","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":null,"percentile":null,"score_date":null},"published_at":"2026-10-28T10:35:30.615Z","modified_at":"2026-10-28T10:35:30.615Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-99176","fetched_at":"2026-10-28T15:55:58.673066Z","source_modified_at":"2026-10-28T10:35:30.615Z"}],"sources":["CVE List"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/d00d5f534a8238674755e59826a6c7d3c8efb870"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/c9716f956216eb74ab0aad7f633586edd49e0322"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/c8f4cfe1cf93bce924e27f2abead7a4c4a487505"}],"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":"2026-10-28T10:35:30.615Z","content_hash":"da714fc57c149bf1cad15977e27d77209b46a83e9c580d03765514f18389a1b5"}}