CVE-2025-40300 (GCVE-0-2025-40300)

Vulnerability from cvelistv5 – Published: 2025-09-11 16:49 – Updated: 2026-10-15 01:09
VLAI
Title
x86/vmscape: Add conditional IBPB mitigation
Summary
In the Linux kernel, the following vulnerability has been resolved: x86/vmscape: Add conditional IBPB mitigation VMSCAPE is a vulnerability that exploits insufficient branch predictor isolation between a guest and a userspace hypervisor (like QEMU). Existing mitigations already protect kernel/KVM from a malicious guest. Userspace can additionally be protected by flushing the branch predictors after a VMexit. Since it is the userspace that consumes the poisoned branch predictors, conditionally issue an IBPB after a VMexit and before returning to userspace. Workloads that frequently switch between hypervisor and userspace will incur the most overhead from the new IBPB. This new IBPB is not integrated with the existing IBPB sites. For instance, a task can use the existing speculation control prctl() to get an IBPB at context switch time. With this implementation, the IBPB is doubled up: one at context switch and another before running userspace. The intent is to integrate and optimize these cases post-embargo. [ dhansen: elaborate on suboptimal IBPB solution ]
Severity
No CVSS data available.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-10 20:41 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6843 records in the last 180 days details
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < ac60717f9a8d21c58617d0b34274babf24135835 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < c08192b5d6730a914dee6175bc71092ee6a65f14 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < d5490dfa35427a2967e00a4c7a1b95fdbc8ede34 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 15006289e5c38b2a830e1fba221977a27598176c (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 893387c18612bb452336a5881da0d015a7e8f4a2 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < f866eef8d1c65504d30923c3f14082ad294d0e6d (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 34e5667041050711a947e260fc9ebebe08bddee5 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < d7ddc93392e4a7ffcccc86edf6ef3e64c778db52 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 459274c77b37ac63b78c928b4b4e748d1f9d05c8 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 510603f504796c3535f67f55fb0b124a303b44c8 (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 9c23a90648e831d611152ac08dbcd1283d405e7f (git)
Affected: 15d45071523d89b3fb7372e2135fbd72f6af9506 , < 2f8f173413f1cbf52660d04df92d0069c4306d25 (git)
Affected: c51f1e5f57cca88d8d5894b6fad1638f643a99d0 (git)
Affected: 4b3870c343a82cd2df7192cc5149c87205dcc611 (git)
Affected: 3.16.57 , < 3.17 (semver)
Affected: 4.4.168 , < 4.5 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 4.16
Unaffected: 0 , < 4.16 (semver)
Unaffected: 5.10.244 , ≤ 5.10.* (semver)
Unaffected: 5.15.193 , ≤ 5.15.* (semver)
Unaffected: 6.1.152 , ≤ 6.1.* (semver)
Unaffected: 6.6.106 , ≤ 6.6.* (semver)
Unaffected: 6.12.47 , ≤ 6.12.* (semver)
Unaffected: 6.16.7 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC CN 4100 Affected: 0 , < V5.0 (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
guessed Create a notification for this product.
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.7 , < * (custom)
guessed Create a notification for this product.
Show details on NVD website

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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nx86/vmscape: Add conditional IBPB mitigation\n\nVMSCAPE is a vulnerability that exploits insufficient branch predictor\nisolation between a guest and a userspace hypervisor (like QEMU). Existing\nmitigations already protect kernel/KVM from a malicious guest. Userspace\ncan additionally be protected by flushing the branch predictors after a\nVMexit.\n\nSince it is the userspace that consumes the poisoned branch predictors,\nconditionally issue an IBPB after a VMexit and before returning to\nuserspace. Workloads that frequently switch between hypervisor and\nuserspace will incur the most overhead from the new IBPB.\n\nThis new IBPB is not integrated with the existing IBPB sites. For\ninstance, a task can use the existing speculation control prctl() to\nget an IBPB at context switch time. With this implementation, the\nIBPB is doubled up: one at context switch and another before running\nuserspace.\n\nThe intent is to integrate and optimize these cases post-embargo.\n\n[ dhansen: elaborate on suboptimal IBPB solution ]"
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            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nx86/vmscape: A\u00f1adir mitigaci\u00f3n condicional de IBPB\n\nVMSCAPE es una vulnerabilidad que explota el aislamiento insuficiente del predictor de ramas entre un invitado y un hipervisor en espacio de usuario (como QEMU). Las mitigaciones existentes ya protegen al kernel/KVM de un invitado malicioso. El espacio de usuario puede protegerse adicionalmente vaciando los predictores de ramas despu\u00e9s de un VMexit.\n\nDado que es el espacio de usuario el que consume los predictores de ramas envenenados, se emite condicionalmente un IBPB despu\u00e9s de un VMexit y antes de regresar al espacio de usuario. Las cargas de trabajo que con frecuencia cambian entre el hipervisor y el espacio de usuario incurrir\u00e1n en la mayor sobrecarga del nuevo IBPB.\n\nEste nuevo IBPB no est\u00e1 integrado con los sitios IBPB existentes. Por ejemplo, una tarea puede usar el prctl() de control de especulaci\u00f3n existente para obtener un IBPB en el momento del cambio de contexto. Con esta implementaci\u00f3n, el IBPB se duplica: uno en el cambio de contexto y otro antes de ejecutar el espacio de usuario.\n\nLa intenci\u00f3n es integrar y optimizar estos casos post-embargo.\n\n[ dhansen: elaborar sobre la soluci\u00f3n IBPB sub\u00f3ptima ]"
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              "url": "https://git.kernel.org/stable/c/ac60717f9a8d21c58617d0b34274babf24135835"
            },
            {
              "url": "https://git.kernel.org/stable/c/c08192b5d6730a914dee6175bc71092ee6a65f14"
            },
            {
              "url": "https://git.kernel.org/stable/c/d5490dfa35427a2967e00a4c7a1b95fdbc8ede34"
            },
            {
              "url": "https://git.kernel.org/stable/c/2f4f2f8f860cb4c3336a7435ebe8dcfded0c9c6e"
            },
            {
              "url": "https://git.kernel.org/stable/c/15006289e5c38b2a830e1fba221977a27598176c"
            },
            {
              "url": "https://git.kernel.org/stable/c/893387c18612bb452336a5881da0d015a7e8f4a2"
            },
            {
              "url": "https://git.kernel.org/stable/c/f866eef8d1c65504d30923c3f14082ad294d0e6d"
            },
            {
              "url": "https://git.kernel.org/stable/c/34e5667041050711a947e260fc9ebebe08bddee5"
            },
            {
              "url": "https://git.kernel.org/stable/c/d7ddc93392e4a7ffcccc86edf6ef3e64c778db52"
            },
            {
              "url": "https://git.kernel.org/stable/c/459274c77b37ac63b78c928b4b4e748d1f9d05c8"
            },
            {
              "url": "https://git.kernel.org/stable/c/510603f504796c3535f67f55fb0b124a303b44c8"
            },
            {
              "url": "https://git.kernel.org/stable/c/9c23a90648e831d611152ac08dbcd1283d405e7f"
            },
            {
              "url": "https://git.kernel.org/stable/c/2f8f173413f1cbf52660d04df92d0069c4306d25"
            }
          ],
          "title": "x86/vmscape: Add conditional IBPB mitigation",
          "x_generator": {
            "engine": "bippy-1.2.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2025-40300",
        "datePublished": "2025-09-11T16:49:24.809Z",
        "dateReserved": "2025-04-16T07:20:57.185Z",
        "dateUpdated": "2026-10-15T01:09:08.416Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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