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CVE-2021-20181

Estado: ModificadaAlta (7.5)—

A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0. This flaw allows a malicious 9p client to cause a use-after-free error, potentially escalating their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity as well as system availability.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (2)

Debian — Debian LinuxQemu — Qemu

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-20181",
  "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": 7.5,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "HIGH",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 6,
        "exploitabilityScore": 0.8
      }
    ]
  },
  "affected": [
    {
      "source": "secalert@redhat.com",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "qemu",
          "versions": [
            {
              "status": "affected",
              "version": "up to, including 5.2.0"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-05-13T16:15:07.653",
  "references": [
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1927007",
      "tags": [
        "Issue Tracking",
        "Patch",
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/02/msg00024.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html",
      "tags": [
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        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
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      "tags": [
        "Third Party Advisory"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://www.zerodayinitiative.com/advisories/ZDI-21-159/",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "secalert@redhat.com"
    },
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1927007",
      "tags": [
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
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      "tags": [
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      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html",
      "tags": [
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        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security.netapp.com/advisory/ntap-20210720-0009/",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.zerodayinitiative.com/advisories/ZDI-21-159/",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "secalert@redhat.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-367"
        }
      ]
    },
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-362"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0. This flaw allows a malicious 9p client to cause a use-after-free error, potentially escalating their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity as well as system availability."
    },
    {
      "lang": "es",
      "value": "Se encontró un fallo de condición de carrera en la implementación del servidor 9pfs de QEMU versiones hasta 5.2.0 incluyéndola. Este fallo permite a un cliente 9p malicioso causar un error de uso de la memoria previamente liberada, escalando potencialmente sus privilegios en el sistema. La mayor amenaza de esta vulnerabilidad es la confidencialidad, la integridad así como la disponibilidad del sistema"
    }
  ],
  "lastModified": "2026-06-17T03:33:25.773",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:qemu:qemu:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "326C44E5-259C-47D1-B540-E153CD7C907C",
              "versionEndIncluding": "5.2.0"
            }
          ],
          "operator": "OR"
        }
      ]
    },
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "DEECE5FC-CACF-4496-A3E7-164736409252"
            },
            {
              "criteria": "cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "07B237A9-69A3-4A9C-9DA0-4E06BD37AE73"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "secalert@redhat.com"
}