Dev error stack trace leaking into prod in Play Framework

Impact

Play Framework, when run in dev mode, shows verbose errors for easy debugging, including an exception stack trace. Play does this by configuring its DefaultHttpErrorHandler to do so based on the application mode. In its Scala API Play also provides a static object DefaultHttpErrorHandler that is configured to always show verbose errors. This is used as a default value in some Play APIs, so it is possible to inadvertently use this version in production. It is also possible to improperly configure the DefaultHttpErrorHandler object instance as the injected error handler. Both of these situations could result in verbose errors displaying to users in a production application, which could expose sensitive information from the application.

In particular the constructor for CORSFilter and apply method for CORSActionBuilder use the static object DefaultHttpErrorHandler as a default value.

Patches

This is patched in Play Framework 2.8.16. The DefaultHttpErrorHandler object has been changed to use the prod-mode behavior, and DevHttpErrorHandler has been introduced for the dev-mode behavior.

Workarounds

When constructing a CORSFilter or CORSActionBuilder, ensure that a properly-configured error handler is passed. Generally this should be done by using the HttpErrorHandler instance provided through dependency injection or through Play’s BuiltInComponents. Ensure that your application is not using the DefaultHttpErrorHandler static object in any code that may be run in production.

References

https://www.playframework.com/documentation/2.8.x/ScalaErrorHandling#Supplying-a-custom-error-handler
https://www.playframework.com/documentation/2.8.x/JavaErrorHandling#Supplying-a-custom-error-handler

For more information

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