CKEditor4 is a widely used, open-source WYSIWYG (What You See Is What You Get) HTML editor, making it easier for content creators to build and edit webpages without requiring deep knowledge of HTML, CSS, or JavaScript. However, CKEditor4 recently encountered a vulnerability in its dialog plugin, which affects versions prior to 4.18.. This vulnerability allows an attacker to exploit a regular expression within the dialog input validator, leading to significant performance degradation and eventually a browser tab freeze.

Exploit Details

The vulnerability lies in the dialog plugin, specifically within the dialog input validator's regular expression. An attacker can craft a malicious string that, when entered into the input field, can cause the matched regular expression to execute in a highly inefficient manner. This results in a significant drop in performance and ultimately leads to the browser tab becoming unresponsive.

In order to take advantage of this vulnerability, an attacker only needs to have access to a website using a vulnerable version of CKEditor4 with the dialog plugin active. The malicious input string could be shared with the target users through various methods, such as public forums or emails with embedded links to the vulnerable site.

Here's a code snippet that demonstrates the vulnerability

// The regular expression in the dialog input validator
var regex = /^(?:(\w+[\w-]*)(?::(\w[\w-]*))?\s*)*(\{[\s\S]*\})?$/;

// A sample malicious input string
var maliciousInput = "AAAAAAAAAAAAAAaa!{{{{#{{{!{}{}{}}}}}BBBBBBBBBBBBBB";

// Execute the test
console.time("vulnerableRegexTest");
regex.test(maliciousInput);
console.timeEnd("vulnerableRegexTest");

This code snippet demonstrates the regular expression vulnerability. When executed with the malicious input string provided, the time taken for the test can be extremely long, eventually causing the browser tab to freeze.

For an in-depth explanation of the vulnerability, you can visit these original references

1. GitHub Issue: Random freeze when using CKEditor4 dialogs
2. CKEditor4 Security Advisory

Mitigation/Patch
The CKEditor4 developers have released a patch for this vulnerability in version 4.18.. Upgrading to CKEditor4 version 4.18. will fix the vulnerability and protect your application from this exploit.

To upgrade, you can follow the instructions provided in the CKEditor4 documentation.

Unfortunately, there are no known workarounds for this vulnerability if you are unable to upgrade to the latest version.

Conclusion

CVE-2022-24729 is a critical vulnerability that affects CKEditor4 versions prior to 4.18., and it can result in significant performance degradation with the possibility of a browser tab freeze. The best way to protect your application against this exploit is to upgrade to CKEditor4 version 4.18. or higher. It is essential to always keep your software up-to-date to minimize the risk of exploits and vulnerabilities.

Timeline

Published on: 03/16/2022 17:15:00 UTC
Last modified on: 07/25/2022 18:21:00 UTC