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CVE-2026-100803

Estado: En análisisAlta (8.1)—

Same-origin policy bypass in the WebExtensions component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

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).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Same-origin policy bypass (CWE-346) requiere interacción del usuario (UI:R) en WebExtensions. Permite acceso a datos de otros orígenes (C:H) y modificación (I:H).

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

User TrainingUser Account ManagementRestrict Web-Based ContentApplication Isolation and SandboxingExploit ProtectionUpdate Software

Tecnologías afectadas (2)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Mozilla — FirefoxAIMozilla — Firefox ESRAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-100803",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-100803",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-10-01T15:15:51.082535Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 8.1,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security@mozilla.org",
      "affectedData": [
        {
          "vendor": "Mozilla",
          "product": "Firefox",
          "versions": [
            {
              "status": "unaffected",
              "version": "115.42",
              "versionType": "rpm",
              "lessThanOrEqual": "115.*"
            },
            {
              "status": "unaffected",
              "version": "140.17",
              "versionType": "rpm",
              "lessThanOrEqual": "140.*"
            },
            {
              "status": "unaffected",
              "version": "153.4",
              "versionType": "rpm",
              "lessThanOrEqual": "153.*"
            },
            {
              "status": "unaffected",
              "version": "157",
              "versionType": "rpm",
              "lessThanOrEqual": "*"
            }
          ]
        },
        {
          "vendor": "Mozilla",
          "product": "Thunderbird",
          "versions": [
            {
              "status": "unaffected",
              "version": "140.17",
              "versionType": "rpm",
              "lessThanOrEqual": "140.*"
            },
            {
              "status": "unaffected",
              "version": "153.4",
              "versionType": "rpm",
              "lessThanOrEqual": "153.*"
            },
            {
              "status": "unaffected",
              "version": "157",
              "versionType": "rpm",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-09-29T13:17:45.390",
  "references": [
    {
      "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2057988",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-100/",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-101/",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-102/",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-103/",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-97/",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-98/",
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2026-99/",
      "source": "security@mozilla.org"
    }
  ],
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "description": [
        {
          "lang": "en",
          "value": "CWE-346"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Same-origin policy bypass in the WebExtensions component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17."
    }
  ],
  "lastModified": "2026-10-01T16:17:29.010",
  "sourceIdentifier": "security@mozilla.org"
}