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CVE-2021-28710

Status: ModifiedHigh (8.8)—

certain VT-d IOMMUs may not work in shared page table mode For efficiency reasons, address translation control structures (page tables) may (and, on suitable hardware, by default will) be shared between CPUs, for second-level translation (EPT), and IOMMUs. These page tables are presently set up to always be 4 levels deep. However, an IOMMU may require the use of just 3 page table levels. In such a configuration the lop level table needs to be stripped before inserting the root table's address into the hardware pagetable base register. When sharing page tables, Xen erroneously skipped this stripping. Consequently, the guest is able to write to leaf page table entries.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (2)

Fedoraproject — FedoraXEN — XEN

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-28710",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.9,
          "accessVector": "LOCAL",
          "vectorString": "AV:L/AC:M/Au:N/C:C/I:C/A:C",
          "authentication": "NONE",
          "integrityImpact": "COMPLETE",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "COMPLETE",
          "confidentialityImpact": "COMPLETE"
        },
        "acInsufInfo": false,
        "impactScore": 10,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 3.4,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 8.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 6,
        "exploitabilityScore": 2
      }
    ]
  },
  "affected": [
    {
      "source": "security@xen.org",
      "affectedData": [
        {
          "vendor": "Xen",
          "product": "xen",
          "versions": [
            {
              "status": "unknown",
              "version": "unspecified",
              "lessThan": "4.12",
              "versionType": "custom"
            },
            {
              "status": "affected",
              "version": "4.15.x",
              "lessThan": "unspecified",
              "versionType": "custom"
            },
            {
              "status": "unaffected",
              "version": "next of xen-unstable",
              "lessThan": "unspecified",
              "versionType": "custom"
            }
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        }
      ]
    }
  ],
  "published": "2021-11-21T15:15:07.597",
  "references": [
    {
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I7ZGWVVRI4XY2XSTBI3XEMWBXPDVX6OT/",
      "source": "security@xen.org"
    },
    {
      "url": "https://security.gentoo.org/glsa/202208-23",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@xen.org"
    },
    {
      "url": "https://xenbits.xenproject.org/xsa/advisory-390.txt",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "security@xen.org"
    },
    {
      "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I7ZGWVVRI4XY2XSTBI3XEMWBXPDVX6OT/",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security.gentoo.org/glsa/202208-23",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://xenbits.xenproject.org/xsa/advisory-390.txt",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-269"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "certain VT-d IOMMUs may not work in shared page table mode For efficiency reasons, address translation control structures (page tables) may (and, on suitable hardware, by default will) be shared between CPUs, for second-level translation (EPT), and IOMMUs. These page tables are presently set up to always be 4 levels deep. However, an IOMMU may require the use of just 3 page table levels. In such a configuration the lop level table needs to be stripped before inserting the root table's address into the hardware pagetable base register. When sharing page tables, Xen erroneously skipped this stripping. Consequently, the guest is able to write to leaf page table entries."
    },
    {
      "lang": "es",
      "value": "determinadas IOMMUs de VT-d pueden no funcionar en modo de tabla de páginas compartida Por razones de eficiencia, las estructuras de control de traducción de direcciones (tablas de páginas) pueden (y, en el hardware adecuado, por defecto) ser compartidas entre las CPUs, para la traducción de segundo nivel (EPT), y las IOMMUs. Estas tablas de páginas están actualmente configuradas para tener siempre 4 niveles de profundidad. Sin embargo, una IOMMU puede requerir el uso de sólo 3 niveles de tabla de páginas. En una configuración de este tipo, la tabla de nivel inferior debe ser eliminada antes de insertar la dirección de la tabla root en el registro base de la tabla de páginas del hardware. Cuando son compartidas las tablas de páginas, Xen omite erróneamente este despojo. En consecuencia, el huésped es capaz de escribir en las entradas de la tabla de páginas hoja"
    }
  ],
  "lastModified": "2026-06-17T03:46:51.003",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:xen:xen:4.15.0:*:*:*:*:*:x86:*",
              "vulnerable": true,
              "matchCriteriaId": "C3BFD203-8E25-46AF-AF43-DAFB86BDFE0D"
            }
          ],
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "criteria": "cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*",
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              "matchCriteriaId": "80E516C0-98A4-4ADE-B69F-66A772E2BAAA"
            }
          ],
          "operator": "OR"
        }
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    }
  ],
  "sourceIdentifier": "security@xen.org"
}