Vulnerabilities
Misconfiguration
Compliance
CVE Vulnerabilities

CVE-2021-21391

Uncontrolled Resource Consumption

Published: Apr 29, 2021 | Modified: Nov 21, 2024
CVSS 3.x
6.5
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CVSS 2.x
4.3 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P
RedHat/V2
RedHat/V3
Ubuntu
MEDIUM
Vulnerability-free packages from our partners
root.io logo minimus.io logo echo.ai logo
Additional information
NVDhttps://nvd.nist.gov/vuln/detail/CVE-2021-21391
CWEhttps://cwe.mitre.org/data/definitions/400.html

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.

Weakness

The product does not properly control the allocation and maintenance of a limited resource.

Affected Software

NameVendorStart VersionEnd Version
Ckeditor5-engineCkeditor*27.0.0 (excluding)
Ckeditor5-fontCkeditor*27.0.0 (excluding)
Ckeditor5-imageCkeditor*27.0.0 (excluding)
Ckeditor5-listCkeditor*27.0.0 (excluding)
Ckeditor5-markdown-gfmCkeditor*27.0.0 (excluding)
Ckeditor5-media-embedCkeditor*27.0.0 (excluding)
Ckeditor5-paste-from-officeCkeditor*27.0.0 (excluding)
Ckeditor5-widgetCkeditor*27.0.0 (excluding)
CkeditorUbuntugroovy*
CkeditorUbuntuhirsute*
CkeditorUbuntutrusty*
CkeditorUbuntuxenial*
Ckeditor3Ubuntubionic*
Ckeditor3Ubuntufocal*
Ckeditor3Ubuntugroovy*
Ckeditor3Ubuntuhirsute*
Ckeditor3Ubuntuimpish*
Ckeditor3Ubuntukinetic*
Ckeditor3Ubuntulunar*
Ckeditor3Ubuntumantic*
Ckeditor3Ubuntuoracular*
Ckeditor3Ubuntuplucky*
Ckeditor3Ubuntutrusty*

Potential Mitigations

  • Mitigation of resource exhaustion attacks requires that the target system either:

  • The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.

  • The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

References

Aqua Security is the largest pure-play cloud native security company, providing customers the freedom to innovate and run their businesses with minimal friction. The Aqua Cloud Native Security Platform provides prevention, detection, and response automation across the entire application lifecycle to secure the build, secure cloud infrastructure and secure running workloads wherever they are deployed.
Copyright © 2026 Aqua Security Software Ltd.   Privacy Policy | Terms of Use