Regular expression Denial of Service in multiple packages
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 security@cksource.com 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 software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @ckeditor/ckeditor5-engine | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-font | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-image | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-list | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-markdown-gfm | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-media-embed | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-paste-from-office | < 27.0.0 | 27.0.0 |
| npm package | @ckeditor/ckeditor5-widget | < 27.0.0 | 27.0.0 |
References
- https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-3rh3-wfr4-76mj
- https://nvd.nist.gov/vuln/detail/CVE-2021-21391
- https://github.com/ckeditor/ckeditor5/releases/tag/v27.0.0
- https://www.npmjs.com/package/@ckeditor/ckeditor5-engine
- https://www.npmjs.com/package/@ckeditor/ckeditor5-font
- https://www.npmjs.com/package/@ckeditor/ckeditor5-image
- https://www.npmjs.com/package/@ckeditor/ckeditor5-list
- https://www.npmjs.com/package/@ckeditor/ckeditor5-markdown-gfm
- https://www.npmjs.com/package/@ckeditor/ckeditor5-media-embed
- https://www.npmjs.com/package/@ckeditor/ckeditor5-paste-from-office
- https://www.npmjs.com/package/@ckeditor/ckeditor5-widget
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- npm
- Package
@ckeditor/ckeditor5-engine, @ckeditor/ckeditor5-font, @ckeditor/ckeditor5-image- Disclosed
- 06.04.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-3rh3-wfr4-76mj - CC BY 4.0
Vulnerability history: @ckeditor/ckeditor5-list
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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