CVE-2026-98471 (GCVE-0-2026-98471)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:15 – Updated: 2026-10-24 14:09
VLAI
Title
KVM: SEV: Do cache maintenance on the source VM during intra-host migration
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6640 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b56639318bb2be66aceba92836279714488709b4 , < 37dfb676fafd1eef36fe0bb649607afbb0d5521b (git)
Affected: b56639318bb2be66aceba92836279714488709b4 , < d4cc2dff12116a700add601c0262132cc26e1b2c (git)
Affected: b56639318bb2be66aceba92836279714488709b4 , < 93de2a6a4b91b72607136dd656edf03fb399d27f (git)
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Linux Linux Affected: 5.16
Unaffected: 0 , < 5.16 (semver)
Unaffected: 6.18.55 , ≤ 6.18.* (semver)
Unaffected: 7.2.9 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/sev.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "status": "affected",
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          "vendor": "Linux",
          "versions": [
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              "version": "5.16"
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              "version": "0",
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              "version": "6.18.55",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2.9",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
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          "nodes": [
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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: SEV: Do cache maintenance on the source VM during intra-host migration\n\nManually perform cache maintenance on the source VM during intra-host\nmigration to ensure no stale data is left in CPU caches after the VM is\ndestroyed.  Because the source VM is \"converted\" to a non-SEV VM, KVM\u0027s\nmemory reclaim flows won\u0027t trigger cache maintenance, e.g. when all guest\nmemory is reclaimed in response to detaching from the mmu_notifier.\n\nNote, relying on the destination VM to do cache maintenance isn\u0027t an option\nas KVM doesn\u0027t require identical guest memory configurations, i.e. the\nsource VM may have access to memory that the destination VM does not.\nEnforcing equivalent memory configurations is infeasible, as it would\nrequire a *deep* comparison of memslots, e.g. to verify that not only are\nthe memslot identical, but what the memslots point at is also identical."
        }
      ],
      "metrics": [
        {
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - A host process reaches patched sev_migrate_from() only through ioctl(KVM_ENABLE_CAP) -\u003e kvm_vm_ioctl_enable_cap_generic() -\u003e kvm_vm_ioctl_enable_cap() with KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM and source/destination VM fds; no network input reaches this path.\nAC:L - The caller can run its SEV source to create dirty guest cache lines, give the destination different memslots, issue MOVE, and unmap source-only RAM; no race or victim-controlled state is required.\nPR:L - The path requires usable /dev/kvm and /dev/sev fds plus both VM fds, but neither kvm_vm_ioctl_enable_cap() nor sev_vm_move_enc_context_from() checks a capability; this is low-privilege KVM/SEV device access, not init-namespace root.\nUI:N - The same VMM process can create and run the source, construct the destination, invoke KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM, and release source-only memory without another user\u0027s action.\nS:U - The attacker invokes a host ioctl and the resulting stale writeback corrupts host-owned memory; this is a local userspace-to-kernel violation, not a guest-to-host escape or IOMMU boundary bypass.\nC:N - sev_writeback_caches() protects against dirty-line writeback; omitting it creates a delayed ciphertext overwrite of reused memory, but the examined path provides no read primitive or way to recover another encryption domain\u0027s plaintext.\nI:H - After sev_migrate_from() clears src-\u003eactive, sev_guest_memory_reclaimed() skips flushing; later eviction of a dirty source-only line can overwrite a full cache line in a page already reassigned to another user, including kernel objects or page tables.\nA:H - The delayed overwrite can corrupt live slab or page-table state and oops or panic the host; the same SEV reclaim-flush mechanism was introduced because repeated malicious allocation and release of unflushed encrypted pages can crash the host."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:00.765Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/37dfb676fafd1eef36fe0bb649607afbb0d5521b"
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        {
          "url": "https://git.kernel.org/stable/c/d4cc2dff12116a700add601c0262132cc26e1b2c"
        },
        {
          "url": "https://git.kernel.org/stable/c/93de2a6a4b91b72607136dd656edf03fb399d27f"
        }
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98471",
    "datePublished": "2026-10-18T15:15:23.690Z",
    "dateReserved": "2026-09-25T10:25:14.351Z",
    "dateUpdated": "2026-10-24T14:09:00.765Z",
    "state": "PUBLISHED"
  },
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  "vulnerability-lookup:meta": {
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      "date": "2026-11-06",
      "epss": "0.00158",
      "percentile": "0.04985"
    },
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      "cve": "CVE-2026-98471",
      "id": "msrc_CVE-2026-98471",
      "initial_release_date": "2026-10-20T01:06:19.000Z",
      "product_status:known_affected": "3",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "KVM: SEV: Do cache maintenance on the source VM during intra-host migration",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98471.json",
      "version": "4"
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    "nvd": {
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                "programFiles": [
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                ],
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SEV: Do cache maintenance on the source VM during intra-host migration\n\nManually perform cache maintenance on the source VM during intra-host\nmigration to ensure no stale data is left in CPU caches after the VM is\ndestroyed.  Because the source VM is \"converted\" to a non-SEV VM, KVM\u0027s\nmemory reclaim flows won\u0027t trigger cache maintenance, e.g. when all guest\nmemory is reclaimed in response to detaching from the mmu_notifier.\n\nNote, relying on the destination VM to do cache maintenance isn\u0027t an option\nas KVM doesn\u0027t require identical guest memory configurations, i.e. the\nsource VM may have access to memory that the destination VM does not.\nEnforcing equivalent memory configurations is infeasible, as it would\nrequire a *deep* comparison of memslots, e.g. to verify that not only are\nthe memslot identical, but what the memslots point at is also identical."
          }
        ],
        "id": "CVE-2026-98471",
        "lastModified": "2026-10-24T14:16:43.463",
        "metrics": {
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                "confidentialityImpact": "NONE",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
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                "userInteraction": "NONE",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "vulnStatus": "Received"
      }
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    "redhat_vex": {
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      "current_release_date": "2026-11-06T03:00:44+00:00",
      "cve": "CVE-2026-98471",
      "id": "CVE-2026-98471",
      "initial_release_date": "2026-10-18T00:00:00+00:00",
      "product_status:known_affected": "160",
      "product_status:known_not_affected": "43",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: KVM: SEV: Do cache maintenance on the source VM during intra-host migration",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98471.json",
      "version": "3"
    }
  }
}



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