CVE-2021-21391

MEDIUM6.5EPSS 1.4%

Regular expression Denial of Service in multiple packages

Published: 4/6/2021Modified: 3/13/2026

Description

### Impact 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. ### Patches The problem has been recognized and patched. The fix will be available in version 27.0.0. ### For more information Email us at [email protected] if you have any questions or comments about this advisory. ### Acknowledgements The CKEditor 5 team would like to thank Yeting Li for recognizing and reporting these vulnerabilities.

Affected packages (8)

npm/@ckeditor/ckeditor5-enginefrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-fontfrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-imagefrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-listfrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-markdown-gfmfrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-media-embedfrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-paste-from-officefrom 0, < 27.0.0
npm/@ckeditor/ckeditor5-widgetfrom 0, < 27.0.0

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	MEDIUM6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Description

Affected packages (8)

CVSS scores

References (11)