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Date: April 28, 2021

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.

Language: JS

Severity Score

Severity Score

Weakness Type (CWE)

Uncontrolled Resource Consumption ('Resource Exhaustion')


Top Fix


Upgrade Version

Upgrade to version @ckeditor/ckeditor5-engine-27.0.0, @ckeditor/ckeditor5-font-27.0.0, @ckeditor/ckeditor5-image-27.0.0, @ckeditor/ckeditor5-list-27.0.0, @ckeditor/ckeditor5-markdown-gfm-27.0.0, @ckeditor/ckeditor5-media-embed-27.0.0, @ckeditor/ckeditor5-paste-from-office-27.0.0, @ckeditor/ckeditor5-widget-27.0.0

Learn More

CVSS v3.1

Base Score:
Attack Vector (AV): NETWORK
Attack Complexity (AC): LOW
Privileges Required (PR): NONE
User Interaction (UI): REQUIRED
Confidentiality (C): NONE
Integrity (I): NONE
Availability (A): HIGH


Base Score:
Access Vector (AV): NETWORK
Access Complexity (AC): MEDIUM
Authentication (AU): NONE
Confidentiality (C): NONE
Integrity (I): NONE
Availability (A): PARTIAL
Additional information:

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