{"api_version":"1","generated_at":"2026-04-22T21:39:03+00:00","cve":"CVE-2021-21391","urls":{"html":"https://cve.report/CVE-2021-21391","api":"https://cve.report/api/cve/CVE-2021-21391.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2021-21391","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-21391"},"summary":{"title":"CVE-2021-21391","description":"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. 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