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CVE-2021-23961

Status: ModifiedHigh (7.4)—

Further techniques that built on the slipstream research combined with a malicious webpage could have exposed both an internal network's hosts as well as services running on the user's local machine. This vulnerability affects Firefox < 85.

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)

Debian — Debian LinuxMozilla — Firefox

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-23961",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4.3,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:P/I:N/A:N",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": true
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 7.4,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 4,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security@mozilla.org",
      "affectedData": [
        {
          "vendor": "Mozilla",
          "product": "Firefox",
          "versions": [
            {
              "status": "affected",
              "version": "< 85"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-02-26T03:15:13.997",
  "references": [
    {
      "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1677940",
      "tags": [
        "Issue Tracking",
        "Permissions Required",
        "Vendor Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/04/msg00019.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/04/msg00020.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://security.gentoo.org/glsa/202104-09",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://security.gentoo.org/glsa/202104-10",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.debian.org/security/2021/dsa-4895",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.debian.org/security/2021/dsa-4897",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-03/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1677940",
      "tags": [
        "Issue Tracking",
        "Permissions Required",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/04/msg00019.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://lists.debian.org/debian-lts-announce/2021/04/msg00020.html",
      "tags": [
        "Mailing List",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security.gentoo.org/glsa/202104-09",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security.gentoo.org/glsa/202104-10",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.debian.org/security/2021/dsa-4895",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.debian.org/security/2021/dsa-4897",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-03/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Further techniques that built on the slipstream research combined with a malicious webpage could have exposed both an internal network's hosts as well as services running on the user's local machine. This vulnerability affects Firefox < 85."
    },
    {
      "lang": "es",
      "value": "Otras técnicas que se basaron en la investigación de slipstream combinada con una página web maliciosa podrían haber expuesto tanto los hosts de una red interna como los servicios que se ejecutan en la máquina local del usuario.&#xa0;Esta vulnerabilidad afecta a Firefox versiones anteriores a 85"
    }
  ],
  "lastModified": "2026-06-17T03:39:04.453",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "403EA47E-6B2D-4082-BFF2-E764C8356854",
              "versionEndExcluding": "85.0"
            }
          ],
          "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": "security@mozilla.org"
}