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FKIE_CVE-2026-72287

Vulnerability from fkie_nvd - Published: 2026-08-15 06:22 - Updated: 2026-08-17 06:18
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: nVMX: Move vTPR vs. TPR Threshold consistency check into "normal" checks Move the off-by-default consistency check for vmcs12.tpr_threshold vs. the virtual APIC vTPR into the "normal" controls checks, as waiting until KVM has loaded some amount of state is unnecessary and actively dangerous. Specifically, failure to unwind vmcs01.GUEST_CR3 to KVM's value when EPT is disabled results in KVM running L1 with an L1-controlled CR3, not with KVM's CR3! Alternatively, KVM could simply reset the MMU to force a reload of vmcs01.GUEST_CR3, but the _only_ reason the check was shoved into a "late" flow was to wait until the vmcs12 pages were retrieved. Rather than build up more crusty code, simply access vTPR using a regular guest memory access (performance isn't a concern). To circumvent the restrictions that led to KVM deferring nested_get_vmcs12_pages(), (a) use a VM-scoped API to read guest memory so that it always hits non-SMM memslots (for RSM), and (b) skip the check (since its off-by-default anyways) when the vCPU doesn't want to run, i.e. when userspace is restoring/stuffing state. If reading guest memory fails, simply skip the consistency check, as KVM's de facto ABI is that VMX instruction accesses to non-existent memory get PCI Bus Error semantics, where reads return 0xFFs. And if vTPR=0xFF, then the vTPR is guaranteed to be greater than or equal to TPR_THRESHOLD.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7d066368f72e6192af7e21c5817626f6da666991
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ebdac7554abb347ca4197be241116842161acd9b
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/vmx/nested.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "7d066368f72e6192af7e21c5817626f6da666991",
              "status": "affected",
              "version": "1100e4910ad207bc00aedc8dfdb228dd1b81f310",
              "versionType": "git"
            },
            {
              "lessThan": "ebdac7554abb347ca4197be241116842161acd9b",
              "status": "affected",
              "version": "1100e4910ad207bc00aedc8dfdb228dd1b81f310",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/vmx/nested.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: nVMX: Move vTPR vs. TPR Threshold consistency check into \"normal\" checks\n\nMove the off-by-default consistency check for vmcs12.tpr_threshold vs.\nthe virtual APIC vTPR into the \"normal\" controls checks, as waiting until\nKVM has loaded some amount of state is unnecessary and actively dangerous.\nSpecifically, failure to unwind vmcs01.GUEST_CR3 to KVM\u0027s value when EPT\nis disabled results in KVM running L1 with an L1-controlled CR3, not with\nKVM\u0027s CR3!\n\nAlternatively, KVM could simply reset the MMU to force a reload of\nvmcs01.GUEST_CR3, but the _only_ reason the check was shoved into a \"late\"\nflow was to wait until the vmcs12 pages were retrieved.  Rather than build\nup more crusty code, simply access vTPR using a regular guest memory access\n(performance isn\u0027t a concern).  To circumvent the restrictions that led to\nKVM deferring nested_get_vmcs12_pages(), (a) use a VM-scoped API to read\nguest memory so that it always hits non-SMM memslots (for RSM), and (b)\nskip the check (since its off-by-default anyways) when the vCPU doesn\u0027t\nwant to run, i.e. when userspace is restoring/stuffing state.\n\nIf reading guest memory fails, simply skip the consistency check, as KVM\u0027s\nde facto ABI is that VMX instruction accesses to non-existent memory get\nPCI Bus Error semantics, where reads return 0xFFs.  And if vTPR=0xFF, then\nthe vTPR is guaranteed to be greater than or equal to TPR_THRESHOLD."
    }
  ],
  "id": "CVE-2026-72287",
  "lastModified": "2026-08-17T06:18:31.437",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.1,
        "impactScore": 6.0,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-08-15T06:22:00.180",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7d066368f72e6192af7e21c5817626f6da666991"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ebdac7554abb347ca4197be241116842161acd9b"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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