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Vulnerability · Published Apr 29, 2021 · Assigned by GitHub_M

CVE-2021-21391Regular expression Denial of Service in multiple packages

Medium 6.5

In plain English

A medium-severity uncontrolled resource consumption in ckeditor5 from ckeditor. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.7% (higher than 77% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)1.7%top 23.1% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official 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. 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Ubuntu:22.04:LTSckeditor3no fix listedUBUNTU-CVE-2021-21391
Ubuntu:24.04:LTSckeditor3no fix listedUBUNTU-CVE-2021-21391
npm@ckeditor/ckeditor5-engine27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-font27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-image27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-list27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-markdown-gfm27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-media-embed27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-paste-from-office27.0.0GHSA-3rh3-wfr4-76mj
npm@ckeditor/ckeditor5-widget27.0.0GHSA-3rh3-wfr4-76mj

Affected products (as reported)

VendorProductVersions
ckeditor ckeditor5 < 27.0.0

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References