CVE-2026-64172 (GCVE-0-2026-64172)
Vulnerability from cvelistv5
Published
2026-07-19 15:40
Modified
2026-08-05 12:39
Severity ?
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235) Hygon Family 18h CPUs are derived from AMD Family 17h (Zen1) silicon and share the same erratum #1235: hardware may read a stale IsRunning=1 bit during ICR write emulation and silently fail to generate an AVIC_IPI_FAILURE_TARGET_NOT_RUNNING VM-Exit on the sending vCPU. The absence of the VM-Exit causes KVM to miss the required wakeup of blocking target vCPUs, leading to hung vCPUs and unbounded delays in guest execution. Extend the existing AMD Family 17h erratum #1235 workaround to also cover Hygon Family 18h. With IPI virtualization disabled, KVM never sets IsRunning=1 in the Physical ID table, so every non-self IPI generates a VM-Exit and is correctly emulated.
References
Impacted products
Vendor Product Version
Linux Linux Version: 8de4a1c8164e5b2e40d1df764840a31de983f40b
Version: 8de4a1c8164e5b2e40d1df764840a31de983f40b
Version: 8de4a1c8164e5b2e40d1df764840a31de983f40b
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/avic.c"
          ],
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          "vendor": "Linux",
          "versions": [
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              "versionType": "git"
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              "version": "8de4a1c8164e5b2e40d1df764840a31de983f40b",
              "versionType": "git"
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        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/avic.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.17"
            },
            {
              "lessThan": "6.17",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.34",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.0.11",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.1",
              "versionType": "original_commit_for_fix"
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      ],
      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.34",
                  "versionStartIncluding": "6.17",
                  "vulnerable": true
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                {
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              "negate": false,
              "operator": "OR"
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        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)\n\nHygon Family 18h CPUs are derived from AMD Family 17h (Zen1) silicon and\nshare the same erratum #1235: hardware may read a stale IsRunning=1 bit\nduring ICR write emulation and silently fail to generate an\nAVIC_IPI_FAILURE_TARGET_NOT_RUNNING VM-Exit on the sending vCPU.\n\nThe absence of the VM-Exit causes KVM to miss the required wakeup of\nblocking target vCPUs, leading to hung vCPUs and unbounded delays in\nguest execution.\n\nExtend the existing AMD Family 17h erratum #1235 workaround to also cover\nHygon Family 18h.  With IPI virtualization disabled, KVM never sets\nIsRunning=1 in the Physical ID table, so every non-self IPI generates a\nVM-Exit and is correctly emulated."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires executing guest code that issues APIC ICR writes against blocking vCPUs; the vulnerable KVM/AVIC path is reached from within a VM, not from remote network packets to the host.\nAC:L - The erratum is a race on IsRunning that the attacker fully controls by pinning one vCPU in a blocking halt/mwait state and having another vCPU send timed IPIs; no conditions outside attacker influence are required once AVIC is active.\nPR:N - No host privileges are needed beyond the ability to run code in a tenant VM on a Hygon KVM host; a cloud customer with a standard VM instance can trigger the bug without host root or special capabilities.\nUI:N - No victim interaction is required; a malicious guest can autonomously orchestrate blocking and IPI traffic to hang vCPUs.\nS:C - In nested virtualization deployments, a malicious L1 hypervisor guest can cause hung vCPUs and unbounded execution delays in L2 guests via the host KVM AVIC path, crossing the L1/L2 security boundary even though there is no host escape.\nC:N - The bug is a missed VM-exit and missed vCPU wakeup with no out-of-bounds access, use-after-free, or information disclosure primitive.\nI:N - No memory or data structures are corrupted; the failure only prevents delivery of required wake events to blocking vCPUs.\nA:H - Missed wakeups cause hung vCPUs and unbounded delays in guest execution, constituting a reliable denial-of-service against VM availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:39:52.348Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/94ade38f317ea086a181db0e6b69c574b3b70a5e"
        },
        {
          "url": "https://git.kernel.org/stable/c/9560e6fee887a9594a89fa265b5b9c79b1591803"
        },
        {
          "url": "https://git.kernel.org/stable/c/9a12fa5213cfc391e0eed63902d3be98f0913765"
        }
      ],
      "title": "KVM: SVM: Disable AVIC IPI virtualization on Hygon Family 18h (erratum #1235)",
      "x_generator": {
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      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64172",
    "datePublished": "2026-07-19T15:40:57.153Z",
    "dateReserved": "2026-07-19T07:54:57.039Z",
    "dateUpdated": "2026-08-05T12:39:52.348Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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