CVE-2026-98639 (GCVE-0-2026-98639)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:20 – Updated: 2026-10-19 09:23
VLAI
Title
KVM: riscv: Fix NACL hfence entry update order
Summary
In the Linux kernel, the following vulnerability has been resolved: KVM: riscv: Fix NACL hfence entry update order The SBI v3.0 specification (section 15.1.2) requires a nested HFENCE entry to be populated as follows: 1) find an unused entry with Config.Pending == 0 2) update the Page_Number and Page_Count words 3) update the Config word with Config.Pending set __kvm_riscv_nacl_hfence() writes the Config word first, so the SBI implementation (or NACL hardware) can observe a pending entry with pnum/pcount values left over from the previous use of that entry, resulting in incorrect TLB flush ranges. Write pnum and pcount first and the Config word last. Since the consumer is an external agent on coherent shared memory, use WRITE_ONCE() to stop the compiler from reordering the stores and smp_wmb() to make the parameter words globally visible before the Pending bit is set.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6820 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d466c19cead5904d4d5d92adb2b213b411d3b849 , < d6de766d8d26d71b714f548192099112def50a9c (git)
Affected: d466c19cead5904d4d5d92adb2b213b411d3b849 , < 6da466502621381fa88a6684290923d25c559266 (git)
Affected: d466c19cead5904d4d5d92adb2b213b411d3b849 , < b3d346838ec65fac7fd83f5dbcedd13cadfffddb (git)
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Linux Linux Affected: 6.13
Unaffected: 0 , < 6.13 (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": {
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          "product": "Linux",
          "programFiles": [
            "arch/riscv/kvm/nacl.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: riscv: Fix NACL hfence entry update order\n\nThe SBI v3.0 specification (section 15.1.2) requires a nested HFENCE\nentry to be populated as follows:\n1) find an unused entry with Config.Pending == 0\n2) update the Page_Number and Page_Count words\n3) update the Config word with Config.Pending set\n\n__kvm_riscv_nacl_hfence() writes the Config word first, so the SBI\nimplementation (or NACL hardware) can observe a pending entry with\npnum/pcount values left over from the previous use of that entry,\nresulting in incorrect TLB flush ranges.\n\nWrite pnum and pcount first and the Config word last. Since the\nconsumer is an external agent on coherent shared memory, use\nWRITE_ONCE() to stop the compiler from reordering the stores and\nsmp_wmb() to make the parameter words globally visible before the\nPending bit is set."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:23:09.004Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/b3d346838ec65fac7fd83f5dbcedd13cadfffddb"
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    "assignerShortName": "Linux",
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    "datePublished": "2026-10-18T15:20:10.591Z",
    "dateReserved": "2026-09-25T10:25:14.361Z",
    "dateUpdated": "2026-10-19T09:23:09.004Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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      "product_status:under_investigation": "1",
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    "nvd": {
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: riscv: Fix NACL hfence entry update order\n\nThe SBI v3.0 specification (section 15.1.2) requires a nested HFENCE\nentry to be populated as follows:\n1) find an unused entry with Config.Pending == 0\n2) update the Page_Number and Page_Count words\n3) update the Config word with Config.Pending set\n\n__kvm_riscv_nacl_hfence() writes the Config word first, so the SBI\nimplementation (or NACL hardware) can observe a pending entry with\npnum/pcount values left over from the previous use of that entry,\nresulting in incorrect TLB flush ranges.\n\nWrite pnum and pcount first and the Config word last. Since the\nconsumer is an external agent on coherent shared memory, use\nWRITE_ONCE() to stop the compiler from reordering the stores and\nsmp_wmb() to make the parameter words globally visible before the\nPending bit is set."
          }
        ],
        "id": "CVE-2026-98639",
        "lastModified": "2026-10-19T10:19:28.133",
        "metrics": {},
        "published": "2026-10-18T16:17:17.020",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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      "source": "Red Hat CSAF VEX",
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      "title": "kernel: KVM: riscv: Fix NACL hfence entry update order",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98639.json",
      "version": "3"
    }
  }
}



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