CVE-2026-98715 (GCVE-0-2026-98715)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:46 – Updated: 2026-10-19 09:24
VLAI
Title
KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN Don't reset the VMCB's TLB control back to "do nothing" on a failed VMRUN, as empirical testing shows that the CPU performs the requested TLB flush if and only if VMRUN is successful, i.e. clearing TLB control on a failed VMRUN effectively drops a TLB flush. Explicitly track the need to flush all ASIDs on a per-CPU basis, as the ASID reuse condition is tied to the pCPU, not to the vCPU. As a bonus, this also obviates the need to avoid clobbering FLUSH_ALL_ASID with TLB_CONTROL_FLUSH_ASID, e.g. in svm_flush_tlb_asid(). Deliberately don't bother saving/restoring the "old" tlb_ctl on failure, in quotes because it's not exactly the old tlb_ctl, it's the tlb_ctl from after pre_svm_run(), but before updating tlb_ctl for flush_all_asids. If VMRUN fails and TLB_CONTROL_FLUSH_ALL_ASID is forced, then the next successful run of the VMCB *may* unnecessarily flush all ASIDs, which strictly speaking could result in noisy neighbor issues. However, the fact that new_asid() is already guest-triggerable, because of KVM's flawed behavior of clearing the ASID on emulated INIT, means that a guest can already trigger a flush of all ASIDs at roughly the same rate. And once KVM stops clobbering the ASID on emulated INIT, *or* assigns a static ASID to each vCPU, this flaw goes away.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6637 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 38e5e92fe8c02a8766459d505423b855caf9af1f , < fd873c3d1b5240e80365f09e758e8c96b88a7cdb (git)
Affected: 38e5e92fe8c02a8766459d505423b855caf9af1f , < 60d93c27859fb3ec5b5a689e24de303f166477d0 (git)
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Linux Linux Affected: 2.6.38
Unaffected: 0 , < 2.6.38 (semver)
Unaffected: 7.2.10 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/svm/svm.c",
            "arch/x86/kvm/svm/svm.h"
          ],
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN\n\nDon\u0027t reset the VMCB\u0027s TLB control back to \"do nothing\" on a failed VMRUN,\nas empirical testing shows that the CPU performs the requested TLB flush if\nand only if VMRUN is successful, i.e. clearing TLB control on a failed\nVMRUN effectively drops a TLB flush.\n\nExplicitly track the need to flush all ASIDs on a per-CPU basis, as the\nASID reuse condition is tied to the pCPU, not to the vCPU.  As a bonus,\nthis also obviates the need to avoid clobbering FLUSH_ALL_ASID with\nTLB_CONTROL_FLUSH_ASID, e.g. in svm_flush_tlb_asid().\n\nDeliberately don\u0027t bother saving/restoring the \"old\" tlb_ctl on failure,\nin quotes because it\u0027s not exactly the old tlb_ctl, it\u0027s the tlb_ctl from\nafter pre_svm_run(), but before updating tlb_ctl for flush_all_asids.  If\nVMRUN fails and TLB_CONTROL_FLUSH_ALL_ASID is forced, then the next\nsuccessful run of the VMCB *may* unnecessarily flush all ASIDs, which\nstrictly speaking could result in noisy neighbor issues.  However, the\nfact that new_asid() is already guest-triggerable, because of KVM\u0027s flawed\nbehavior of clearing the ASID on emulated INIT, means that a guest can\nalready trigger a flush of all ASIDs at roughly the same rate.  And once\nKVM stops clobbering the ASID on emulated INIT, *or* assigns a static ASID\nto each vCPU, this flaw goes away."
        }
      ],
      "providerMetadata": {
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        "shortName": "Linux"
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    "datePublished": "2026-10-18T15:46:47.988Z",
    "dateReserved": "2026-09-25T10:25:14.366Z",
    "dateUpdated": "2026-10-19T09:24:26.247Z",
    "state": "PUBLISHED"
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      "id": "msrc_CVE-2026-98715",
      "initial_release_date": "2026-10-20T01:08:01.000Z",
      "product_status:known_affected": "2",
      "product_status:under_investigation": "1",
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      "status": "final",
      "title": "KVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN",
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      "version": "4"
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Preserve TLB control (i.e. pending TLB flush) on failed VMRUN\n\nDon\u0027t reset the VMCB\u0027s TLB control back to \"do nothing\" on a failed VMRUN,\nas empirical testing shows that the CPU performs the requested TLB flush if\nand only if VMRUN is successful, i.e. clearing TLB control on a failed\nVMRUN effectively drops a TLB flush.\n\nExplicitly track the need to flush all ASIDs on a per-CPU basis, as the\nASID reuse condition is tied to the pCPU, not to the vCPU.  As a bonus,\nthis also obviates the need to avoid clobbering FLUSH_ALL_ASID with\nTLB_CONTROL_FLUSH_ASID, e.g. in svm_flush_tlb_asid().\n\nDeliberately don\u0027t bother saving/restoring the \"old\" tlb_ctl on failure,\nin quotes because it\u0027s not exactly the old tlb_ctl, it\u0027s the tlb_ctl from\nafter pre_svm_run(), but before updating tlb_ctl for flush_all_asids.  If\nVMRUN fails and TLB_CONTROL_FLUSH_ALL_ASID is forced, then the next\nsuccessful run of the VMCB *may* unnecessarily flush all ASIDs, which\nstrictly speaking could result in noisy neighbor issues.  However, the\nfact that new_asid() is already guest-triggerable, because of KVM\u0027s flawed\nbehavior of clearing the ASID on emulated INIT, means that a guest can\nalready trigger a flush of all ASIDs at roughly the same rate.  And once\nKVM stops clobbering the ASID on emulated INIT, *or* assigns a static ASID\nto each vCPU, this flaw goes away."
          }
        ],
        "id": "CVE-2026-98715",
        "lastModified": "2026-10-19T10:19:35.747",
        "metrics": {},
        "published": "2026-10-18T16:17:25.050",
        "references": [
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      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98715.json",
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}



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