{"id":"CVE-2026-99176","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=\u003eL2 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   \u003cTASK\u003e\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   \u003c/TASK\u003e\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]","modified":"2026-11-01T02:32:07.268955335Z","published":"2026-10-28T10:35:30.615Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/99xxx/CVE-2026-99176.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/6a36b05fc5b3d660fcc826133dc92e2fc87bd1de"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c2586874605ec23b611c57fe71d183d98f168971"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c611337aee17a0627e365e58e2b6e78803fb3c36"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c8f4cfe1cf93bce924e27f2abead7a4c4a487505"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c9716f956216eb74ab0aad7f633586edd49e0322"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d00d5f534a8238674755e59826a6c7d3c8efb870"},{"type":"WEB","url":"https://git.kernel.org/stable/c/df4d01be5b318024bec68654c7af0ebc0e0ed8a1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f0c077c36fda9d498db39199e3997860e985efc8"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/99xxx/CVE-2026-99176.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99176"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"72e9cbdb43384ceacc49e2fb6b8c8fb7c5988778"},{"fixed":"c2586874605ec23b611c57fe71d183d98f168971"},{"fixed":"c611337aee17a0627e365e58e2b6e78803fb3c36"},{"fixed":"df4d01be5b318024bec68654c7af0ebc0e0ed8a1"},{"fixed":"6a36b05fc5b3d660fcc826133dc92e2fc87bd1de"},{"fixed":"f0c077c36fda9d498db39199e3997860e985efc8"},{"fixed":"d00d5f534a8238674755e59826a6c7d3c8efb870"},{"fixed":"c9716f956216eb74ab0aad7f633586edd49e0322"},{"fixed":"c8f4cfe1cf93bce924e27f2abead7a4c4a487505"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-99176.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.15.0"},{"fixed":"5.10.273"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.224"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.191"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.161"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.115"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.59"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.13"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-99176.json"}}],"schema_version":"1.9.2"}