CKEditor 5 Markdown plugin Regular expression Denial of Service
Impact
A regular expression denial of service (ReDoS) vulnerability has been discovered in the CKEditor 5 Markdown plugin code. The vulnerability allowed to abuse a link recognition regular expression, which could cause a significant performance drop resulting in a browser tab freeze. It affects all users using the CKEditor 5 Markdown plugin at version <= 24.0.0.
Patches
The problem has been recognized and patched. The fix will be available in version 25.0.0.
Workarounds
The user can work around the issue by:
- Upgrading CKEditor 5 to version 25.0.0.
- Disabling the Markdown plugin.
More information
If you have any questions or comments about this advisory:
- Email us at security@cksource.com
Acknowledgements
The CKEditor 5 team would like to thank Erik Krogh Kristensen from the GitHub team for recognizing this vulnerability and Alvaro Muñoz from GitHub for reporting it.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @ckeditor/ckeditor5-markdown-gfm | < 25.0.0 | 25.0.0 |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-400- Platform
- npm
- Package
@ckeditor/ckeditor5-markdown-gfm- Disclosed
- 29.01.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-hgmg-hhc8-g5wr - CC BY 4.0
Vulnerability history: @ckeditor/ckeditor5-markdown-gfm
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 01.2021 08.2022
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 3
Disclosures per year
- 2021: 2
- 2022: 1
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
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