Resource exhaustion in Ckeditor Ckeditor5

CVE-2021-21391

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.

Vulnerability class: DoS (Denial of Service)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.017 (75.8th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 76th percentile — 75.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2021-21391: held from 0.017 to 0.017.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: 0.000

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2021-21391?
CVE-2021-21391 is a medium-severity vulnerability in Ckeditor Ckeditor5, classified under Uncontrolled Resource Consumption. CVSS score: 6.5/10. Published 2021-04-29.
How severe is CVE-2021-21391?
Medium severity. CVSS v3 base score is 6.5 out of 10.
Is CVE-2021-21391 known to be exploited?
1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.