CVE-2026-64247 (GCVE-0-2026-64247)
Vulnerability from cvelistv5
Published
2026-07-24 15:31
Modified
2026-08-17 04:51
Severity ?
8.4 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: hyper-v: Bound the bank index when querying sparse banks When checking if a VP ID is included in a sparse bank set, explicitly check that the ID can actually be contained in a sparse bank (the TLFS allows for a maximum of 64 banks of 64 vCPUs each). When handling a paravirtual TLB flush for L2, the VP ID is copied verbatim from the enlightened VMCS, without any bounds check, i.e. isn't guaranteed to be under the limit of 4096. Failure to check the bounds of the VP ID leads to an out-of-bounds read when testing the sparse bank, and super strictly speaking could lead to KVM performing an unnecessary TLB flush for an L2 vCPU. ================================================================== BUG: KASAN: use-after-free in hv_is_vp_in_sparse_set+0x85/0x100 [kvm] Read of size 8 at addr ffff88811ba5f598 by task hyperv_evmcs/2802 CPU: 12 UID: 1000 PID: 2802 Comm: hyperv_evmcs Not tainted 7.1.0-rc2 #7 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dump_stack_lvl+0x51/0x60 print_report+0xcb/0x5d0 kasan_report+0xb4/0xe0 kasan_check_range+0x35/0x1b0 hv_is_vp_in_sparse_set+0x85/0x100 [kvm] kvm_hv_flush_tlb+0xe9e/0x16c0 [kvm] kvm_hv_hypercall+0xe6b/0x1e60 [kvm] vmx_handle_exit+0x485/0x1b60 [kvm_intel] kvm_arch_vcpu_ioctl_run+0x22e3/0x5070 [kvm] kvm_vcpu_ioctl+0x5d0/0x10c0 [kvm] __x64_sys_ioctl+0x129/0x1a0 do_syscall_64+0xb9/0xcf0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f0e62d1a9bf </TASK> The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffffffffffffffff pfn:0x11ba5f flags: 0x4000000000000000(zone=1) raw: 4000000000000000 0000000000000000 00000000ffffffff 0000000000000000 raw: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88811ba5f480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88811ba5f500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff88811ba5f580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88811ba5f600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88811ba5f680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== Disabling lock debugging due to kernel taint Opportunistically add a compile time assertion to ensure the maximum number of sparse banks exactly matches the number of possible bits in the passed in mask. [sean: add KASAN splat, drop comment, add assert, massage changelog]
References
Impacted products
Vendor Product Version
Linux Linux Version: c58a318f6090efe06e6702b8882e2026f44f620e
Version: c58a318f6090efe06e6702b8882e2026f44f620e
Version: c58a318f6090efe06e6702b8882e2026f44f620e
Version: c58a318f6090efe06e6702b8882e2026f44f620e
Version: c58a318f6090efe06e6702b8882e2026f44f620e
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/hyperv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "d18756b12aab30d07794446445c93112e5c69a2e",
              "status": "affected",
              "version": "c58a318f6090efe06e6702b8882e2026f44f620e",
              "versionType": "git"
            },
            {
              "lessThan": "83c2f52c6a78b1590034e955cff3fe0b052fe4ae",
              "status": "affected",
              "version": "c58a318f6090efe06e6702b8882e2026f44f620e",
              "versionType": "git"
            },
            {
              "lessThan": "e36095d8d922bb26ce860231aacf0cd14edea07c",
              "status": "affected",
              "version": "c58a318f6090efe06e6702b8882e2026f44f620e",
              "versionType": "git"
            },
            {
              "lessThan": "f636cf6a1e7b7f40d48d8d08bd5f152aa61dd130",
              "status": "affected",
              "version": "c58a318f6090efe06e6702b8882e2026f44f620e",
              "versionType": "git"
            },
            {
              "lessThan": "4721f8160f17554b003e8928bb61e6c9b2fe92a3",
              "status": "affected",
              "version": "c58a318f6090efe06e6702b8882e2026f44f620e",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "arch/x86/kvm/hyperv.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.2"
            },
            {
              "lessThan": "6.2",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.144",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.95",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.38",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.144",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.95",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.38",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.3",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: hyper-v: Bound the bank index when querying sparse banks\n\nWhen checking if a VP ID is included in a sparse bank set, explicitly check\nthat the ID can actually be contained in a sparse bank (the TLFS allows for\na maximum of 64 banks of 64 vCPUs each).  When handling a paravirtual TLB\nflush for L2, the VP ID is copied verbatim from the enlightened VMCS,\nwithout any bounds check, i.e. isn\u0027t guaranteed to be under the limit of\n4096.\n\nFailure to check the bounds of the VP ID leads to an out-of-bounds read\nwhen testing the sparse bank, and super strictly speaking could lead to KVM\nperforming an unnecessary TLB flush for an L2 vCPU.\n\n  ==================================================================\n  BUG: KASAN: use-after-free in hv_is_vp_in_sparse_set+0x85/0x100 [kvm]\n  Read of size 8 at addr ffff88811ba5f598 by task hyperv_evmcs/2802\n\n  CPU: 12 UID: 1000 PID: 2802 Comm: hyperv_evmcs Not tainted 7.1.0-rc2 #7 PREEMPT\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015\n  Call Trace:\n   \u003cTASK\u003e\n   dump_stack_lvl+0x51/0x60\n   print_report+0xcb/0x5d0\n   kasan_report+0xb4/0xe0\n   kasan_check_range+0x35/0x1b0\n   hv_is_vp_in_sparse_set+0x85/0x100 [kvm]\n   kvm_hv_flush_tlb+0xe9e/0x16c0 [kvm]\n   kvm_hv_hypercall+0xe6b/0x1e60 [kvm]\n   vmx_handle_exit+0x485/0x1b60 [kvm_intel]\n   kvm_arch_vcpu_ioctl_run+0x22e3/0x5070 [kvm]\n   kvm_vcpu_ioctl+0x5d0/0x10c0 [kvm]\n   __x64_sys_ioctl+0x129/0x1a0\n   do_syscall_64+0xb9/0xcf0\n   entry_SYSCALL_64_after_hwframe+0x4b/0x53\n  RIP: 0033:0x7f0e62d1a9bf\n   \u003c/TASK\u003e\n\n  The buggy address belongs to the physical page:\n  page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffffffffffffffff pfn:0x11ba5f\n  flags: 0x4000000000000000(zone=1)\n  raw: 4000000000000000 0000000000000000 00000000ffffffff 0000000000000000\n  raw: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000000\n  page dumped because: kasan: bad access detected\n\n  Memory state around the buggy address:\n   ffff88811ba5f480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n   ffff88811ba5f500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n  \u003effff88811ba5f580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n                              ^\n   ffff88811ba5f600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n   ffff88811ba5f680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n  ==================================================================\n  Disabling lock debugging due to kernel taint\n\nOpportunistically add a compile time assertion to ensure the maximum number\nof sparse banks exactly matches the number of possible bits in the passed\nin mask.\n\n[sean: add KASAN splat, drop comment, add assert, massage changelog]"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Triggering requires a Hyper-V TLB-flush hypercall from an L2 vCPU under KVM, ultimately reached through the local KVM_RUN ioctl; no network path reaches it.\nAC:L - A malicious nested-virtualization tenant controls both the unchecked enlightened-VMCS/VMCB VP ID and the sparse-bank hypercall data, with no uncontrollable race required.\nPR:L - The attacker needs control of a KVM guest with nested virtualization, or ordinary /dev/kvm access to create one, but requires neither host root nor an init-namespace capability.\nUI:N - Once the crafted nested guest executes, no action by another user is required.\nS:C - The out-of-bounds access occurs in the host kernel from attacker-controlled guest state, crossing the KVM guest-to-host isolation boundary.\nC:H - The attacker-selected VP ID makes test_bit() query selectable bits far beyond the stack-resident 64-bit mask, and the resulting TLB-flush decision can provide an oracle for host kernel memory.\nI:N - The primitive performs reads only; a set result merely selects a legitimate L2 vCPU for an extra TLB flush, with no out-of-bounds write or unsafe mapping change.\nA:H - The selectable access can reach a VMAP_STACK guard or another unmapped page and oops the host; KASAN already detects the access as an eight-byte invalid read, which can become a host-wide denial of service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:51:58.515Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/d18756b12aab30d07794446445c93112e5c69a2e"
        },
        {
          "url": "https://git.kernel.org/stable/c/83c2f52c6a78b1590034e955cff3fe0b052fe4ae"
        },
        {
          "url": "https://git.kernel.org/stable/c/e36095d8d922bb26ce860231aacf0cd14edea07c"
        },
        {
          "url": "https://git.kernel.org/stable/c/f636cf6a1e7b7f40d48d8d08bd5f152aa61dd130"
        },
        {
          "url": "https://git.kernel.org/stable/c/4721f8160f17554b003e8928bb61e6c9b2fe92a3"
        }
      ],
      "title": "KVM: x86: hyper-v: Bound the bank index when querying sparse banks",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64247",
    "datePublished": "2026-07-24T15:31:15.304Z",
    "dateReserved": "2026-07-19T15:36:31.772Z",
    "dateUpdated": "2026-08-17T04:51:58.515Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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