CVE-2026-99017 (GCVE-0-2026-99017)

Vulnerability from cvelistv5 – Published: 2026-10-23 12:20 – Updated: 2026-10-24 14:10
VLAI
Title
riscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE
Summary
In the Linux kernel, the following vulnerability has been resolved: riscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE errata_probe_ghostwrite() only marks the CPU as vulnerable when it is called at the RISCV_ALTERNATIVES_EARLY_BOOT stage, and the mitigation in ghostwrite_enable_mitigation() only takes effect if the vulnerable state was recorded before the boot alternatives are patched. The early boot stage is only executed when CONFIG_RISCV_ALTERNATIVE_EARLY is enabled, which currently is only selected by ERRATA_THEAD_MAE. In a kernel built with ERRATA_THEAD_GHOSTWRITE=y but ERRATA_THEAD_MAE=n, the early alternatives never run, so ghostwrite_state is never set to VULNERABLE: ghostwrite_enable_mitigation() returns false, xtheadvector remains enabled, and sysfs reports "Not affected" on a vulnerable T-Head C9xx CPU. Select RISCV_ALTERNATIVE_EARLY from ERRATA_THEAD_GHOSTWRITE so that the vulnerability is detected in the early boot stage and the default mitigation is applied.
Severity
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7056 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 4bf97069239bcfca9840936313c7ac35a6e04488 , < fa465a7819ecbe5801b78c088d3cadaf2664b8ca (git)
Affected: 4bf97069239bcfca9840936313c7ac35a6e04488 , < 7fee577a2fa78b9a76da015beec1ccf978746ebb (git)
Affected: 4bf97069239bcfca9840936313c7ac35a6e04488 , < 298510bbc7c3017c0faf481c6ea66f1065b657b4 (git)
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Linux Linux Affected: 6.14
Unaffected: 0 , < 6.14 (semver)
Unaffected: 6.18.57 , ≤ 6.18.* (semver)
Unaffected: 7.2.11 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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              "versionType": "semver"
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              "operator": "OR"
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        {
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE\n\nerrata_probe_ghostwrite() only marks the CPU as vulnerable when it is\ncalled at the RISCV_ALTERNATIVES_EARLY_BOOT stage, and the mitigation\nin ghostwrite_enable_mitigation() only takes effect if the vulnerable\nstate was recorded before the boot alternatives are patched.\n\nThe early boot stage is only executed when CONFIG_RISCV_ALTERNATIVE_EARLY\nis enabled, which currently is only selected by ERRATA_THEAD_MAE. In a\nkernel built with ERRATA_THEAD_GHOSTWRITE=y but ERRATA_THEAD_MAE=n, the\nearly alternatives never run, so ghostwrite_state is never set to\nVULNERABLE: ghostwrite_enable_mitigation() returns false, xtheadvector\nremains enabled, and sysfs reports \"Not affected\" on a vulnerable\nT-Head C9xx CPU.\n\nSelect RISCV_ALTERNATIVE_EARLY from ERRATA_THEAD_GHOSTWRITE so that the\nvulnerability is detected in the early boot stage and the default\nmitigation is applied."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - A local process executes the GhostWrite vector sequence; its first vector instruction follows handle_exception() through do_trap_insn_illegal() to riscv_v_first_use_handler(), after which the faulty store executes in U-mode. No network protocol carries the causal input.\nAC:H - Exposure requires a vulnerable T-Head C9xx with xtheadvector and the unusual build combination ERRATA_THEAD_GHOSTWRITE=y plus ERRATA_THEAD_MAE=n; both errata options default to y, and an attacker cannot create this kernel configuration.\nPR:L - riscv_v_first_use_handler() and riscv_v_vstate_ctrl_set_current() contain no capability check, so an ordinary local user can enable vector state and execute the sequence; no administrative privilege or user namespace is required.\nUI:N - The attacking process itself enables or first-uses vector state and executes the faulty store; no victim must mount media, open a file, or perform another action.\nS:U - The missed disable_xtheadvector() call lets a user process escalate into the kernel on the same host; this is a local user-to-kernel privilege escalation under the host\u0027s existing security authority.\nC:H - Leaving xtheadvector enabled exposes GhostWrite\u0027s arbitrary physical-write primitive; overwriting a PTE\u0027s page-frame number creates an arbitrary physical-read mapping covering kernel and other-process memory.\nI:H - Because ghostwrite_enable_mitigation() returns false without the early VULNERABLE state, faulty high-order vector stores remain usable for attacker-chosen byte writes to physical memory, including PTEs and kernel or machine-mode code.\nA:H - The same unrestricted physical writes can corrupt kernel text, page tables, or device MMIO, causing an unrecoverable kernel crash or system hang."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:10:04.808Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/fa465a7819ecbe5801b78c088d3cadaf2664b8ca"
        },
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          "url": "https://git.kernel.org/stable/c/7fee577a2fa78b9a76da015beec1ccf978746ebb"
        },
        {
          "url": "https://git.kernel.org/stable/c/298510bbc7c3017c0faf481c6ea66f1065b657b4"
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      ],
      "title": "riscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99017",
    "datePublished": "2026-10-23T12:20:53.518Z",
    "dateReserved": "2026-09-25T10:25:14.386Z",
    "dateUpdated": "2026-10-24T14:10:04.808Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-10-24",
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      "percentile": "0.10159"
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                "programFiles": [
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nriscv: errata: select RISCV_ALTERNATIVE_EARLY for THEAD GHOSTWRITE\n\nerrata_probe_ghostwrite() only marks the CPU as vulnerable when it is\ncalled at the RISCV_ALTERNATIVES_EARLY_BOOT stage, and the mitigation\nin ghostwrite_enable_mitigation() only takes effect if the vulnerable\nstate was recorded before the boot alternatives are patched.\n\nThe early boot stage is only executed when CONFIG_RISCV_ALTERNATIVE_EARLY\nis enabled, which currently is only selected by ERRATA_THEAD_MAE. In a\nkernel built with ERRATA_THEAD_GHOSTWRITE=y but ERRATA_THEAD_MAE=n, the\nearly alternatives never run, so ghostwrite_state is never set to\nVULNERABLE: ghostwrite_enable_mitigation() returns false, xtheadvector\nremains enabled, and sysfs reports \"Not affected\" on a vulnerable\nT-Head C9xx CPU.\n\nSelect RISCV_ALTERNATIVE_EARLY from ERRATA_THEAD_GHOSTWRITE so that the\nvulnerability is detected in the early boot stage and the default\nmitigation is applied."
          }
        ],
        "id": "CVE-2026-99017",
        "lastModified": "2026-10-24T14:16:52.790",
        "metrics": {
          "cvssMetricV31": [
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "vulnStatus": "Received"
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    }
  }
}



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