Default development error handler in Ratpack is vulnerable to HTML content injection (XSS)

Versions of Ratpack from 0.9.10 through 1.7.5 are vulnerable to CWE-79: Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’) (aka. XSS) in the development error handler. An attacker can utilize this to perform XSS when an exception message contains untrusted data.

As a simplistic example:

RatpackServer startedServer = RatpackServer.start(server -> {
    server.handlers(chain -> chain.all(ctx -> {
        // User supplied query parameter
        String message = ctx.getRequest().getQueryParams().get("message");
        // User supplied data appended to the message in an exception
        throw new RuntimeException("An error occurred: " + message);
    }));
});

Impact

• Cross-Site Scripting

Patches

This vulnerability has been patched in Ratpack version 1.7.6.

Workarounds

If you are unable to update your version of Ratpack, we recommend the following workarounds and mitigations.

• Ensure that development mode is disabled in production.
• Don’t use real customer data (ie. untrusted user input) in development.

References

• Ratpack development mode
• Code Patch - a3cbb13

For more information

If you have any questions or comments about this advisory:

• Open an issue in ratpack/ratpack
• Ask in our Slack channel