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CVE-2021-21391— Regular expression Denial of Service in multiple packages

Quick assessment

Affected
ckeditor ckeditor5
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

CKEditor是一套开源的、基于网页的文字编辑器。 CKEditor 5 存在资源管理错误漏洞，该漏洞源于一个正则表达式拒绝服务（ReDoS）漏洞。该漏洞允许滥用特定的正则表达式，这可能会导致性能显着下降，从而导致浏览器选项卡冻结。

CVSS 6.5 · Medium EPSS 1.67% · P75

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
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I. Basic Information for CVE-2021-21391

Vulnerability Information
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Vulnerability Title
Regular expression Denial of Service in multiple packages
Source: CVE Program / CVE List V5
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
CKEditor 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
CKEditor是一套开源的、基于网页的文字编辑器。 CKEditor 5 存在资源管理错误漏洞，该漏洞源于一个正则表达式拒绝服务（ReDoS）漏洞。该漏洞允许滥用特定的正则表达式，这可能会导致性能显着下降，从而导致浏览器选项卡冻结。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ckeditor ckeditor5 < 27.0.0 -

II. Public POCs for CVE-2021-21391

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III. Intelligence Information for CVE-2021-21391

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Vendor Advisories for CVE-2021-21391 (1)

Other References for CVE-2021-21391 (7)

IV. Related Vulnerabilities

Same product: ckeditor5
Same vendor: ckeditor
Same weakness: CWE-400

V. Comments for CVE-2021-21391

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