Home/CVE/CKEditor 5 provides a WYSIWYG editing solution. This CVE affects the following npm packages: ckeditor5-engine, ckeditor5
CVE

CVE-2021-21391

CKEditor 5 provides a WYSIWYG editing solution. This CVE affects the following npm packages: ckeditor5-engine, ckeditor5

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.

MEDIUM · CVSS 6.5 EPSS 0.01354
Monitor
  • No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-400Uncontrolled Resource Consumption
▤

Affected Products & Versions

8
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
▤

Affected Packages

8
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
npm @ckeditor/ckeditor5-engine MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-font MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-image MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-list MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-markdown-gfm MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-media-embed MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-paste-from-office MODERATE fixed in 27.0.0
npm @ckeditor/ckeditor5-widget MODERATE fixed in 27.0.0
▣

Scoring & Timeline

6.5
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD29 Apr 2021 · 01:15 AM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
🔗

References & Sources

9
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-3rh3-wfr4-76mjThird Party Advisory
https://www.npmjs.com/package/%40ckeditor/ckeditor5-engine
https://www.npmjs.com/package/%40ckeditor/ckeditor5-font
https://www.npmjs.com/package/%40ckeditor/ckeditor5-image
https://www.npmjs.com/package/%40ckeditor/ckeditor5-list
https://www.npmjs.com/package/%40ckeditor/ckeditor5-markdown-gfm
Intelligence Graph · click any node to traverse
CVETechnique ActorTool Family
drag to reposition · click any node to traverse · button top-right enlarges
External lookups - second-class, for what we don’t hold ourselves
NVDCVE.orgCISAVulnersExploit-DBGitHub PoCVulnCheck KEVGreyNoise
Vulnerabilities
CISA KEV catalog
CWE weaknesses
CAPEC attack patterns
Package vulnerabilities
Threat intelligence
Threat actors
Tools & malware
ATT&CK techniques
IOCs
Detection & defense
Sigma rules
YARA rules
Atomic Red Team tests
D3FEND countermeasures
Compliance
NIST 800-53
ISO 27001:2022
SOC 2 TSC
PCI-DSS v4.0
CIS Controls v8.1
About
All capabilities
Live statistics
Data sources
Privacy policy
Terms of service
threatengine.sh  ·  Open-source threat intelligence platform  ·  100+ authoritative sources  ·  Every fact traces to its origin