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CVE-2021-1855

Status: ModifiedMedium (6.5)—

A logic issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.3. A malicious website may be able to force unnecessary network connections to fetch its favicon.

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)

Apple — Macos

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-1855",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.4,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:P/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 4.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 6.5,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.5,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "product-security@apple.com",
      "affectedData": [
        {
          "vendor": "Apple",
          "product": "macOS",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "11.3",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-09-08T15:15:11.403",
  "references": [
    {
      "url": "https://support.apple.com/en-us/HT212325",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "product-security@apple.com"
    },
    {
      "url": "https://support.apple.com/en-us/HT212325",
      "tags": [
        "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": "A logic issue was addressed with improved state management. This issue is fixed in macOS Big Sur 11.3. A malicious website may be able to force unnecessary network connections to fetch its favicon."
    },
    {
      "lang": "es",
      "value": "Se abordó un problema lógico con una administración de estado mejorada. Este problema se corrigió en macOS Big Sur versión 11.3. Un sitio web malicioso puede forzar conexiones de red innecesarias para obtener su favicon"
    }
  ],
  "lastModified": "2026-06-17T03:32:40.350",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:apple:macos:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "4E699CCC-31F5-458E-A59C-79B3AF143747",
              "versionEndExcluding": "11.3",
              "versionStartIncluding": "11.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "product-security@apple.com"
}