Overview
A critical cross-site scripting (XSS) vulnerability, identified as CVE-2025-63830, has been discovered in CKFinder version 1.4.3. This vulnerability allows attackers to inject malicious scripts into the application through the file upload functionality. Specifically, by uploading a specially crafted SVG file containing active content, an attacker can execute arbitrary JavaScript code within the context of a user’s browser who interacts with the uploaded file.
Technical Details
The vulnerability resides in the way CKFinder 1.4.3 handles SVG files during the upload process. The application fails to properly sanitize or validate the uploaded SVG content, allowing an attacker to embed malicious JavaScript within the SVG image. When a user accesses or previews the uploaded SVG file, the embedded JavaScript code is executed, potentially leading to session hijacking, defacement, or other malicious activities. The exploitation involves crafting an SVG file with an <script> tag or other methods to execute JavaScript on the client-side.
Here’s a basic example of a malicious SVG file that could be used to exploit this vulnerability:
<svg xmlns="http://www.w3.org/2000/svg" onload="alert('XSS Vulnerability!')">
<script>
// Your malicious JavaScript code here
</script>
</svg>
CVSS Analysis
Currently, the CVSS score and severity for CVE-2025-63830 are listed as N/A. However, given the nature of XSS vulnerabilities and their potential impact, this vulnerability should be considered high risk and addressed promptly. A successful XSS attack can have significant consequences for users and the application itself. We strongly advise monitoring the NVD (National Vulnerability Database) for updates on the CVSS score as it becomes available.
Possible Impact
A successful exploitation of this XSS vulnerability can have several severe consequences, including:
- Session Hijacking: Attackers can steal user session cookies, allowing them to impersonate legitimate users and gain unauthorized access to sensitive data.
- Defacement: Attackers can modify the content of the web page, displaying malicious or misleading information to users.
- Phishing Attacks: Attackers can redirect users to phishing websites to steal their credentials or other sensitive information.
- Malware Distribution: Attackers can inject malicious code that downloads and installs malware on users’ computers.
- Data Theft: Attackers can steal sensitive data stored within the application or accessed by users.
Mitigation or Patch Steps
To mitigate this vulnerability, we recommend the following steps:
- Upgrade CKFinder: The primary mitigation step is to upgrade to a version of CKFinder that addresses this vulnerability. Consult the CKFinder changelog and documentation for the latest secure version. Unfortunately, since CKFinder 1.4.3 is quite old, upgrading to a newer version in the CKFinder 3 or CKFinder 4 line is the recommended action.
- Input Validation and Sanitization: Implement strict input validation and sanitization measures to prevent malicious code from being injected into SVG files. Ensure that all user-supplied data is properly encoded before being displayed on the page.
- Content Security Policy (CSP): Implement a Content Security Policy (CSP) to restrict the sources from which the browser can load resources. This can help prevent the execution of malicious JavaScript code injected by attackers.
- File Type Validation: Implement robust file type validation to ensure that only legitimate SVG files are accepted. Reject files with suspicious content or file extensions.
