6.5
MEDIUM
CVE-2021-21391
CKEditor 5 Regular Expression Denial of Service Vulnerability
Description

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.

INFO

Published Date :

April 29, 2021, 1:15 a.m.

Last Modified :

Nov. 7, 2023, 3:30 a.m.

Remotely Exploitable :

Yes !

Impact Score :

3.6

Exploitability Score :

2.8
Public PoC/Exploit Available at Github

CVE-2021-21391 has a 1 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

Affected Products

The following products are affected by CVE-2021-21391 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Ckeditor ckeditor5
2 Ckeditor ckeditor5-engine
3 Ckeditor ckeditor5-font
4 Ckeditor ckeditor5-image
5 Ckeditor ckeditor5-list
6 Ckeditor ckeditor5-markdown-gfm
7 Ckeditor ckeditor5-media-embed
8 Ckeditor ckeditor5-paste-from-office
9 Ckeditor ckeditor5-widget

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

List of RegEx DoS (ReDoS) CVEs and resources

security awesome redos regex dos regex-dos pentesting awesome-list regex-security

Updated: 2 months, 3 weeks ago
23 stars 2 fork 2 watcher
Born at : June 10, 2021, 1:57 a.m. This repo has been linked 76 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-21391 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2021-21391 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • CVE Modified by [email protected]

    Nov. 07, 2023

    Action Type Old Value New Value
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-markdown-gfm [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-engine [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-font [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-image [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-list [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-media-embed [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-paste-from-office [No types assigned]
    Added Reference GitHub, Inc. https://www.npmjs.com/package/%40ckeditor/ckeditor5-widget [No types assigned]
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-markdown-gfm
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-engine
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-image
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-media-embed
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-list
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-font
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-paste-from-office
    Removed Reference GitHub, Inc. https://www.npmjs.com/package/@ckeditor/ckeditor5-widget
  • Initial Analysis by [email protected]

    May. 10, 2021

    Action Type Old Value New Value
    Added CVSS V2 Metadata Victim must voluntarily interact with attack mechanism
    Added CVSS V2 NIST (AV:N/AC:M/Au:N/C:N/I:N/A:P)
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
    Changed Reference Type https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-3rh3-wfr4-76mj No Types Assigned https://github.com/ckeditor/ckeditor5/security/advisories/GHSA-3rh3-wfr4-76mj Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-engine No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-engine Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-font No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-font Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-image No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-image Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-list No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-list Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-markdown-gfm No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-markdown-gfm Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-media-embed No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-media-embed Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-paste-from-office No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-paste-from-office Product, Third Party Advisory
    Changed Reference Type https://www.npmjs.com/package/@ckeditor/ckeditor5-widget No Types Assigned https://www.npmjs.com/package/@ckeditor/ckeditor5-widget Product, Third Party Advisory
    Added CPE Configuration OR *cpe:2.3:a:ckeditor:ckeditor5-engine:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-font:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-image:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-list:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-markdown-gfm:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-media-embed:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-paste-from-office:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0 *cpe:2.3:a:ckeditor:ckeditor5-widget:*:*:*:*:*:node.js:*:* versions up to (excluding) 27.0.0
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-21391 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2021-21391 weaknesses.

Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

0.48 }} 0.06%

score

0.73307

percentile

CVSS31 - Vulnerability Scoring System
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability