GHSA-3rh3-wfr4-76mj — medium GitHub Advisory (CVE-2021-21391) in npm/@ckeditor/ckeditor5-engine

Description

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 [email protected] 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.

Basic information

Type: reviewed
Severity: medium
Advisory on GitHub: Open advisory ↗
Repository advisory: Open repository advisory ↗
Source code: Not specified
Published (advisory): 2021-04-06 17:28:41 UTC
Updated: 2023-02-01 05:05:16 UTC
GitHub reviewed: 2021-03-31 18:37:46 UTC
NVD published: 2021-04-28

Score	Percentile
8.30%	92.10%

CVSS Scores

Base score	Version	Severity	Vector
6.5	3.1	—	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.

Identifiers

Type	Value
GHSA	GHSA-3rh3-wfr4-76mj ↗
CVE	CVE-2021-21391 ↗

CWEs

CWE id	Name
CWE-400	Uncontrolled Resource Consumption

Affected packages (8)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem	Package	Vulnerable range	First patched	Vulnerable functions
npm	@ckeditor/ckeditor5-engine	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-font	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-image	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-list	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-markdown-gfm	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-media-embed	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-paste-from-office	<= 26.0.0	27.0.0	—
npm	@ckeditor/ckeditor5-widget	<= 26.0.0	27.0.0	—

Regular expression Denial of Service in multiple packages