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CVE-2021-27889

Estado: ModificadaMedia (6.1)—💥 Exploit

Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages.

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).

💥 Exploits públicos

Hay código de explotación o plantillas de detección públicos. No es lo mismo que explotación activa confirmada (KEV), pero aumenta el riesgo: parchee con prioridad.

Tecnologías afectadas (1)

Mybb — Mybb

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-27889",
  "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:N/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "NONE"
        },
        "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": 6.1,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "integrityImpact": "LOW",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 2.7,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-03-15T17:15:22.517",
  "references": [
    {
      "url": "http://packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.html",
      "tags": [
        "Exploit",
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://blog.sonarsource.com/mybb-remote-code-execution-chain",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcm",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "http://packetstormsecurity.com/files/161908/MyBB-1.8.25-Remote-Command-Execution.html",
      "tags": [
        "Exploit",
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://blog.sonarsource.com/mybb-remote-code-execution-chain",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/mybb/mybb/security/advisories/GHSA-xhj7-3349-mqcm",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Cross-site Scripting (XSS) vulnerability in MyBB before 1.8.26 via Nested Auto URL when parsing messages."
    },
    {
      "lang": "es",
      "value": "Una vulnerabilidad de tipo Cross-site Scripting (XSS) en MyBB versiones anteriores a  1.8.26 a través de Nested Auto URL cuando se analizan los mensajes"
    }
  ],
  "lastModified": "2026-06-17T03:45:33.900",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:mybb:mybb:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E92578FF-AAA5-4F8F-8D78-0662DB9BB02C",
              "versionEndExcluding": "1.8.26"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}