CVE-2022-24729 is a medium-severity vulnerability affecting CKEditor4, an open-source WYSIWYG HTML editor widely used in web applications for content creation and editing. The vulnerability resides specifically in the 'dialog' plugin of CKEditor4 versions prior to 4.18.0. It stems from an uncontrolled resource consumption issue (CWE-400) caused by the abuse of a dialog input validator implemented via a regular expression. When malicious input is processed by this validator, it can trigger excessive CPU usage leading to significant performance degradation, ultimately causing the browser tab to freeze. This is a classic example of a Regular Expression Denial of Service (ReDoS) attack vector, where crafted input exploits the inefficiency of the regex engine, resulting in resource exhaustion. The vulnerability does not require authentication or user interaction beyond loading or interacting with the vulnerable dialog component, making exploitation feasible in scenarios where CKEditor4 is embedded in web pages accessible to untrusted users. There are no known workarounds, but the vendor has released a patch in version 4.18.0 that addresses this issue by presumably optimizing or replacing the vulnerable regular expression. No exploits have been reported in the wild to date, but the nature of the vulnerability means it could be leveraged to disrupt availability of web applications using affected CKEditor4 versions.

For European organizations, the primary impact of this vulnerability is on availability. Web applications that integrate vulnerable CKEditor4 versions could be subjected to denial-of-service conditions, where attackers submit crafted inputs to freeze users' browser tabs, effectively disrupting normal operations. This can degrade user experience, reduce productivity, and potentially cause reputational damage if public-facing services are affected. While confidentiality and integrity are not directly compromised by this vulnerability, the availability impact can have cascading effects, especially for organizations relying on CKEditor4 for critical content management or collaborative editing platforms. Sectors such as media, education, government portals, and enterprise intranets that utilize CKEditor4 extensively are at risk. The ease of exploitation without authentication means that any exposed CKEditor4 instance is a potential target. Given the widespread use of CKEditor4 in Europe, particularly in countries with strong digital public services and e-government initiatives, the risk is non-trivial. However, the absence of known active exploits reduces immediate threat levels, though proactive patching is essential to prevent future attacks.

European organizations should prioritize upgrading CKEditor4 instances to version 4.18.0 or later to apply the official patch that resolves the uncontrolled resource consumption vulnerability. Since no workarounds exist, patching is the primary mitigation strategy. Additionally, organizations should implement input validation and sanitization at the application level to limit the complexity and size of inputs submitted to CKEditor dialogs, reducing the risk of triggering the vulnerable regex. Web application firewalls (WAFs) can be configured to detect and block suspicious payloads that resemble ReDoS attack patterns targeting CKEditor dialogs. Monitoring application performance metrics and browser error logs can help detect attempted exploitation attempts early. For public-facing services, rate limiting and CAPTCHA challenges on input forms that invoke CKEditor dialogs can further reduce attack surface. Finally, organizations should conduct an inventory of all web applications using CKEditor4 to ensure no vulnerable versions remain in production or staging environments.