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CVE-2021-21254

Estado: ModificadaMedia (6.5)—

CKEditor 5 is an open source rich text editor framework with a modular architecture. The CKEditor 5 Markdown plugin (@ckeditor/ckeditor5-markdown-gfm) before version 25.0.0 has a regex denial of service (ReDoS) vulnerability. The vulnerability allowed to abuse link recognition regular expression, which could cause a significant performance drop resulting in browser tab freeze. It affects all users using CKEditor 5 Markdown plugin at version <= 24.0.0. The problem has been recognized and patched. The fix will be available in version 25.0.0.

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).

Tecnologías afectadas (1)

Ckeditor — Ckeditor5

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2021-21254",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:S/C:N/I:N/A:P",
          "authentication": "SINGLE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 6.5,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.8
      },
      {
        "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:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "ckeditor",
          "product": "ckeditor5",
          "versions": [
            {
              "status": "affected",
              "version": "< 25.0.0"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-01-29T22:15:14.797",
  "references": [
    {
      "url": "https://github.com/ckeditor/ckeditor5/releases/tag/v25.0.0",
      "tags": [
        "Release Notes",
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-hgmg-hhc8-g5wr",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://www.npmjs.com/package/%40ckeditor/ckeditor5-markdown-gfm",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/ckeditor/ckeditor5/releases/tag/v25.0.0",
      "tags": [
        "Release Notes",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-hgmg-hhc8-g5wr",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.npmjs.com/package/%40ckeditor/ckeditor5-markdown-gfm",
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-400"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "CKEditor 5 is an open source rich text editor framework with a modular architecture. The CKEditor 5 Markdown plugin (@ckeditor/ckeditor5-markdown-gfm) before version 25.0.0 has a regex denial of service (ReDoS) vulnerability. The vulnerability allowed to abuse link recognition regular expression, which could cause a significant performance drop resulting in browser tab freeze. It affects all users using CKEditor 5 Markdown plugin at version <= 24.0.0. The problem has been recognized and patched. The fix will be available in version 25.0.0."
    },
    {
      "lang": "es",
      "value": "CKEditor 5 es un framework de edición de texto enriquecido de código abierto con una arquitectura modular.&#xa0;El plugin CKEditor 5 Markdown (@ckeditor/ckeditor5-markdown-gfm) anterior a versión 25.0.0, presenta una vulnerabilidad de denegación de servicio de expresiones regulares  (ReDoS).&#xa0;La vulnerabilidad permitió abusar de la expresión regular de reconocimiento de enlace, lo que podría causar una caída significativa en el rendimiento resultando en la congelación de la pestaña del navegador.&#xa0;Afecta a todos los usuarios que usan el plugin CKEditor 5 Markdown en la versión anterior a 24.0.0 e incluyéndola.&#xa0;El problema ha sido reconocido y parcheado.&#xa0;La corrección estará disponible en la versión 25.0.0"
    }
  ],
  "lastModified": "2026-06-17T03:35:08.190",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:ckeditor:ckeditor5:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "8B47943C-76FE-4852-86F0-14CA6F0BD30D",
              "versionEndExcluding": "25.0.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security-advisories@github.com"
}