Denial of service binding form from JSON in Play Framework

Impact

A denial-of-service vulnerability has been discovered in Play’s forms library, in both the Scala and Java APIs. This can occur when using either the Form#bindFromRequest method on a JSON request body or the Form#bind method directly on a JSON value. If the JSON data being bound to the form contains a deeply-nested JSON object or array, the form binding implementation may consume all available heap space and cause an OutOfMemoryError. If executing on the default dispatcher and akka.jvm-exit-on-fatal-error is enabled—as it is by default—then this can crash the application process.

Form.bindFromRequest is vulnerable when using any body parser that produces a type of AnyContent or JsValue in Scala, or one that can produce a JsonNode in Java. This includes Play’s default body parser.

Patches

This vulnerability been patched in version 2.8.16. There is now a global limit on the depth of a JSON object that can be parsed, which can be configured by the user if necessary.

Workarounds

Applications that do not need to parse a request body of type application/json can switch from the default body parser to another body parser that supports only the specific type of body they expect; for example, the formUrlEncoded body parser can be used if the Play action only needs to accept application/x-www-form-urlencoded.