Reflected Cross-Site Scripting in Vaadin 10 and 11-13

Background

Vaadin is an open-source Java framework used for building web applications. It provides a set of user interface components and tools for creating modern and responsive web interfaces. The Vaadin framework is vulnerable to a reflected cross-site scripting (XSS) attack in the default RouteNotFoundError view. This vulnerability affects versions 10.0.0 through 10.0.13 (Vaadin 10) and 11.0.0 through 13.0.5 (Vaadin 11-13).

Vulnerability Detail

The vulnerability arises due to missing output sanitization in the default RouteNotFoundError view. An attacker can exploit this by crafting a malicious URL that injects and executes arbitrary JavaScript code in the context of the victim's browser. This can lead to various consequences, such as stealing sensitive information, performing actions on behalf of the victim, or manipulating the web page content.

Workaround

If upgrading the package is not immediately feasible, a temporary workaround is to manually sanitize the output in the RouteNotFoundError view. This can be done by applying appropriate output encoding or escaping techniques to any user-controlled data that is displayed in the view. Here is an example of how to sanitize the output using the Java OWASP Encoder library:

import org.owasp.encoder.Encode;

public class RouteNotFoundErrorView extends View {
  @Override
  public void onAttach(AttachEvent event) {
    String errorMessage = getErrorMessageFromRequest();
    String sanitizedErrorMessage = Encode.forHtml(errorMessage);
    // Display the sanitized error message
  }
}

Conclusion

The reflected cross-site scripting vulnerability in Vaadin 10 and 11-13 can allow an attacker to execute arbitrary JavaScript code in the victim's browser. To mitigate this risk, it is crucial to upgrade to the fixed versions of the com.vaadin:flow-server package. Alternatively, manual sanitization of the output in the RouteNotFoundError view can be applied as a temporary workaround. For further assistance and support in vulnerability remediation, please contact DevNack.com.

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