CVE-2021-21391 Explained : Impact and Mitigation

CKEditor 5 provides a WYSIWYG editing solution. This CVE affects multiple CKEditor 5 npm packages due to a regular expression denial of service (ReDoS) vulnerability. Users of CKEditor 5 versions <= 26.0.0 are at risk of experiencing significant performance issues, including browser tab freeze. The vulnerability has been patched in version 27.0.0.

Understanding CVE-2021-21391

This section will provide insights into the impact, technical details, and mitigation strategies related to the regular expression DoS vulnerability in CKEditor 5 packages.

What is CVE-2021-21391?

CVE-2021-21391 is a vulnerability affecting CKEditor 5 npm packages that could lead to a browser tab freeze due to a regular expression denial of service vulnerability. The issue impacts versions of the affected packages up to 26.0.0.

The Impact of CVE-2021-21391

The vulnerability allows threat actors to abuse specific regular expressions, causing a performance drop and potentially freezing the browser tab. CKEditor 5 users on versions <= 26.0.0 are urged to update to version 27.0.0 to mitigate this risk.

Technical Details of CVE-2021-21391

This section will delve into the technical aspects of the vulnerability, including its description, affected systems and versions, and exploitation mechanism.

Vulnerability Description

The ReDoS vulnerability in CKEditor 5 npm packages allows attackers to exploit certain regular expressions, resulting in a significant performance degradation and potential browser tab freezing.

Affected Systems and Versions

CKEditor 5 packages including ckeditor5-engine, ckeditor5-font, ckeditor5-image, ckeditor5-list, ckeditor5-markdown-gfm, ckeditor5-media-embed, ckeditor5-paste-from-office, and ckeditor5-widget are impacted by CVE-2021-21391 up to version 26.0.0.

Exploitation Mechanism

Threat actors can abuse specific regular expressions in the affected packages, leading to a performance drop that may freeze the browser tab.

Mitigation and Prevention

In this section, we will outline immediate steps to take, best security practices, and the importance of patching and updates in safeguarding against CVE-2021-21391.

Immediate Steps to Take

Users of CKEditor 5 packages should update to version 27.0.0 to patch the ReDoS vulnerability and prevent potential browser tab freezes.

Long-Term Security Practices

Practicing secure coding, implementing input validation, and keeping software up to date are crucial long-term security measures to mitigate the risk of DoS vulnerabilities.

Patching and Updates

Regularly updating CKEditor 5 packages to the latest version is essential in addressing known vulnerabilities and ensuring a secure development environment.