CVE-2022-31175 in CKEditor 5
Summary
by MITRE • 08/03/2022
CKEditor 5 is a JavaScript rich text editor. A cross-site scripting vulnerability has been discovered affecting three optional CKEditor 5's packages in versions prior to 35.0.1. The vulnerability allowed to trigger a JavaScript code after fulfilling special conditions. The affected packages are `@ckeditor/ckeditor5-markdown-gfm`, `@ckeditor/ckeditor5-html-support`, and `@ckeditor/ckeditor5-html-embed`. The specific conditions are 1) Using one of the affected packages. In case of `ckeditor5-html-support` and `ckeditor5-html-embed`, additionally, it was required to use a configuration that allows unsafe markup inside the editor. 2) Destroying the editor instance and 3) Initializing the editor on an element and using an element other than `<textarea>` as a base. The root cause of the issue was a mechanism responsible for updating the source element with the markup coming from the CKEditor 5 data pipeline after destroying the editor. This vulnerability might affect a small percent of integrators that depend on dynamic editor initialization/destroy and use Markdown, General HTML Support or HTML embed features. The problem has been recognized and patched. The fix is available in version 35.0.1. There are no known workarounds for this issue.
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Analysis
by VulDB Data Team • 08/04/2022
The CVE-2022-31175 vulnerability represents a cross-site scripting vulnerability within CKEditor 5 that specifically impacts three optional packages: ckeditor/ckeditor5-markdown-gfm, ckeditor/ckeditor5-html-support, and @ckeditor/ckeditor5-html-embed. This vulnerability stems from improper handling of markup data during the editor lifecycle, particularly when editors are destroyed and reinitialized. The flaw manifests when developers utilize the affected packages in conjunction with specific configuration settings that permit unsafe markup processing, creating a pathway for malicious script execution.
The technical exploitation requires a precise sequence of conditions that must be met for the vulnerability to be triggered. First, developers must implement one of the affected packages within their CKEditor 5 integration. For the html-support and html-embed packages, additional configuration is necessary to enable unsafe markup processing. Second, the editor instance must be destroyed through the standard destruction mechanism. Finally, the editor must be reinitialized on an element that is not a textarea, typically involving div or other container elements. The root cause lies in the mechanism responsible for updating the source element with markup from CKEditor 5's data pipeline after editor destruction, where input validation fails to properly sanitize the markup content.
This vulnerability aligns with CWE-79, Cross-site Scripting, and follows patterns consistent with ATT&CK technique T1203, Exploitation for Client Execution, where malicious code execution occurs through web browser interfaces. The operational impact affects a minority of CKEditor 5 users who implement dynamic editor initialization and destruction patterns combined with the specific features that handle external markup. The vulnerability is particularly concerning because it operates through legitimate editor functionality rather than requiring unusual user interactions, making it more likely to be exploited in production environments where dynamic content management is common.
The security implications extend beyond simple script injection, as successful exploitation could enable attackers to execute arbitrary JavaScript within the context of the victim's browser session. This could lead to session hijacking, data exfiltration, or further exploitation through browser-based attack vectors. The affected packages process markup content from external sources, creating potential injection points when the editor's data pipeline updates the source element after destruction. The patch implemented in version 35.0.1 addresses the core issue by strengthening input validation and sanitization within the editor's data pipeline mechanism. Organizations using CKEditor 5 should immediately upgrade to version 35.0.1 or later, as no effective workarounds exist for this vulnerability. The fix specifically targets the source element update mechanism that was vulnerable to improper markup handling, ensuring that all content is properly sanitized before being written back to the DOM element. This remediation addresses the fundamental flaw in how CKEditor 5 processes and updates markup content during the editor destruction and reinitialization cycle, providing comprehensive protection against this cross-site scripting vulnerability.