ubuntu-cve-2021-21391
Vulnerability from osv_ubuntu
Published
2021-04-29 01:15
Modified
2026-01-20 04:58
Summary
Details

CKEditor 5 provides a WYSIWYG editing solution. This CVE affects the following npm packages: ckeditor5-engine, ckeditor5-font, ckeditor5-image, ckeditor5-list, ckeditor5-markdown-gfm, ckeditor5-media-embed, ckeditor5-paste-from-office, and ckeditor5-widget. Following an internal audit, a regular expression denial of service (ReDoS) vulnerability has been discovered in multiple CKEditor 5 packages. The vulnerability allowed to abuse particular regular expressions, which could cause a significant performance drop resulting in a browser tab freeze. It affects all users using the CKEditor 5 packages listed above at version <= 26.0.0. The problem has been recognized and patched. The fix will be available in version 27.0.0.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
N/A (UNKNOWN)
medium
References
To clipboard 

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ckeditor3",
            "binary_version": "3.6.6.1+dfsg-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:18.04:LTS",
        "name": "ckeditor3",
        "purl": "pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-1?arch=source\u0026distro=bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.6.6.1+dfsg-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ckeditor3",
            "binary_version": "3.6.6.1+dfsg-4"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "ckeditor3",
        "purl": "pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-4?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.6.6.1+dfsg-3",
        "3.6.6.1+dfsg-4"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ckeditor3",
            "binary_version": "3.6.6.1+dfsg-7"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "ckeditor3",
        "purl": "pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-7?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.6.6.1+dfsg-7"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "ckeditor3",
            "binary_version": "3.6.6.1+dfsg-7"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "ckeditor3",
        "purl": "pkg:deb/ubuntu/ckeditor3@3.6.6.1+dfsg-7?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "3.6.6.1+dfsg-7"
      ]
    }
  ],
  "aliases": [],
  "details": "CKEditor 5 provides a WYSIWYG editing solution. This CVE affects the following npm packages: ckeditor5-engine, ckeditor5-font, ckeditor5-image, ckeditor5-list, ckeditor5-markdown-gfm, ckeditor5-media-embed, ckeditor5-paste-from-office, and ckeditor5-widget. Following an internal audit, a regular expression denial of service (ReDoS) vulnerability has been discovered in multiple CKEditor 5 packages. The vulnerability allowed to abuse particular regular expressions, which could cause a significant performance drop resulting in a browser tab freeze. It affects all users using the CKEditor 5 packages listed above at version \u003c= 26.0.0. The problem has been recognized and patched. The fix will be available in version 27.0.0.",
  "id": "UBUNTU-CVE-2021-21391",
  "modified": "2026-01-20T04:58:17Z",
  "published": "2021-04-29T01:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-21391"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-markdown-gfm"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-engine"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-image"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-media-embed"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-3rh3-wfr4-76mj"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-list"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-font"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-paste-from-office"
    },
    {
      "type": "REPORT",
      "url": "https://www.npmjs.com/package/@ckeditor/ckeditor5-widget"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2021-21391"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2021-21391"
  ]
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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