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CVE-2017-7821

Status: ModifiedCritical (9.8)—

A vulnerability where WebExtensions can download and attempt to open a file of some non-executable file types. This can be triggered without specific user interaction for the file download and open actions. This could be used to trigger known vulnerabilities in the programs that handle those document types. This vulnerability affects Firefox < 56.

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 (1)

Mozilla — Firefox

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2017-7821",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 7.5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "HIGH",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV30": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.0",
          "baseScore": 9.8,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security@mozilla.org",
      "affectedData": [
        {
          "vendor": "Mozilla",
          "product": "Firefox",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "56",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2018-06-11T21:29:10.920",
  "references": [
    {
      "url": "http://www.securityfocus.com/bid/101057",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "http://www.securitytracker.com/id/1039465",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1346515",
      "tags": [
        "Exploit",
        "Issue Tracking"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2017-21/",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "http://www.securityfocus.com/bid/101057",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "http://www.securitytracker.com/id/1039465",
      "tags": [
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1346515",
      "tags": [
        "Exploit",
        "Issue Tracking"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2017-21/",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-732"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A vulnerability where WebExtensions can download and attempt to open a file of some non-executable file types. This can be triggered without specific user interaction for the file download and open actions. This could be used to trigger known vulnerabilities in the programs that handle those document types. This vulnerability affects Firefox < 56."
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad en el que WebExtensions puede descargar e intentar abrir un archivo de tipos que no sean ejecutables. Esto se puede desencadenar sin la interacción expresa del usuario para las acciones de descarga y apertura de archivos. Esto se podría utilizar para provocar vulnerabilidades conocidas en los programas que manipula dichos tipos de documentos. Esta vulnerabilidad afecta a las versiones anteriores a la 56 de Firefox."
    }
  ],
  "lastModified": "2026-06-17T01:25:16.903",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "FEC7D85F-EE10-4144-B49D-DC88DE61352E",
              "versionEndIncluding": "55.0.3"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security@mozilla.org"
}