{
  "threat_severity" : "Important",
  "public_date" : "2026-04-01T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: Linux kernel KVM: Privilege escalation or denial of service due to improper shadow page table entry handling",
    "id" : "2453803",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2453803"
  },
  "cvss3" : {
    "cvss3_base_score" : "8.1",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-416",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nKVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE\nWhen installing an emulated MMIO SPTE, do so *after* dropping/zapping the\nexisting SPTE (if it's shadow-present).  While commit a54aa15c6bda3 was\nright about it being impossible to convert a shadow-present SPTE to an\nMMIO SPTE due to a _guest_ write, it failed to account for writes to guest\nmemory that are outside the scope of KVM.\nE.g. if host userspace modifies a shadowed gPTE to switch from a memslot\nto emulted MMIO and then the guest hits a relevant page fault, KVM will\ninstall the MMIO SPTE without first zapping the shadow-present SPTE.\n------------[ cut here ]------------\nis_shadow_present_pte(*sptep)\nWARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292\nModules linked in: kvm_intel kvm irqbypass\nCPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\nRIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm]\nCall Trace:\n<TASK>\nmmu_set_spte+0x237/0x440 [kvm]\nept_page_fault+0x535/0x7f0 [kvm]\nkvm_mmu_do_page_fault+0xee/0x1f0 [kvm]\nkvm_mmu_page_fault+0x8d/0x620 [kvm]\nvmx_handle_exit+0x18c/0x5a0 [kvm_intel]\nkvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm]\nkvm_vcpu_ioctl+0x2d5/0x980 [kvm]\n__x64_sys_ioctl+0x8a/0xd0\ndo_syscall_64+0xb5/0x730\nentry_SYSCALL_64_after_hwframe+0x4b/0x53\nRIP: 0033:0x47fa3f\n</TASK>\n---[ end trace 0000000000000000 ]---", "A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) component. A local attacker with privileges on the host system could exploit a vulnerability in how KVM handles shadow page table entries (SPTEs) during memory-mapped I/O (MMIO) operations. By manipulating guest page table entries (gPTEs) from host userspace, an attacker could cause KVM to install an MMIO SPTE without properly removing an existing shadow-present SPTE. This improper handling could lead to a kernel warning, resulting in a denial of service or potentially allowing for privilege escalation or information disclosure." ],
  "statement" : "This is an Important impact vulnerability. A flaw in the KVM's x86/mmu component in the Linux kernel could allow a privileged guest user to trigger a host denial of service. This issue occurs when host userspace modifies a shadowed gPTE to switch from a memslot to emulated MMIO, leading to a missing SPTE zap. Red Hat Enterprise Linux 8, 9, and 10, and Red Hat In-Vehicle OS are affected. Red Hat Enterprise Linux 6 and 7 are not affected.",
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-23401\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-23401\nhttps://lore.kernel.org/linux-cve-announce/2026040108-CVE-2026-23401-956d@gregkh/T" ],
  "name" : "CVE-2026-23401",
  "csaw" : false
}