CVE-2021-21254 : Exploit Details and Defense Strategies

CKEditor 5 Markdown plugin (@ckeditor/ckeditor5-markdown-gfm) before version 25.0.0 has a regex denial of service (ReDoS) vulnerability. This could lead to a significant performance drop resulting in browser tab freeze for users on affected versions. Learn more about the impact, technical details, and mitigation steps below.

Understanding CVE-2021-21254

This section provides insights into the nature of the CVE-2021-21254 vulnerability.

What is CVE-2021-21254?

CVE-2021-21254 refers to a ReDoS vulnerability in the CKEditor 5 Markdown plugin before version 25.0.0. It allows attackers to abuse the link recognition regular expression, leading to a performance degradation issue that can freeze browser tabs.

The Impact of CVE-2021-21254

The vulnerability affects users utilizing the CKEditor 5 Markdown plugin at version 24.0.0 and below. It has a base score of 6.5, classified as medium severity due to its potential impact on availability, especially for network-based attacks.

Technical Details of CVE-2021-21254

Explore the technical aspects of the CVE-2021-21254 vulnerability for a better understanding.

Vulnerability Description

The vulnerability arises from a regex denial of service (ReDoS) issue that enables malicious actors to exploit the link recognition regular expression within the CKEditor 5 Markdown plugin.

Affected Systems and Versions

Users of CKEditor 5 Markdown plugin with versions equal to or below 24.0.0 are susceptible to this vulnerability.

Exploitation Mechanism

Attackers can trigger the vulnerability by submitting crafted input that abuses the link recognition regular expression, leading to performance degradation and potential browser tab freezing.

Mitigation and Prevention

Discover the steps to mitigate and prevent exploitation of CVE-2021-21254.

Immediate Steps to Take

Users are advised to update their CKEditor 5 Markdown plugin to version 25.0.0 or higher to mitigate the ReDoS vulnerability and prevent performance issues.

Long-Term Security Practices

Implementing regular software updates and security patches is crucial to maintaining a secure environment and preventing future vulnerabilities.

Patching and Updates

Ensure timely installation of patches and updates provided by CKEditor to address security issues and enhance the overall stability of the Markdown plugin.