Static resource cache poisoning in Spring MVC and WebFlux

Spring MVC and WebFlux applications are vulnerable to cache poisoning when resolving static resources.

More precisely, an application can be vulnerable when all the following are true:

* the application is using Spring MVC or Spring WebFlux

* the application is configuring the  resource chain support https://docs.spring.io/spring-framework/reference/web/webmvc/mvc-config/static-resources.html#page-title  with caching enabled

* the application adds support for encoded resources resolution

* the resource cache must be empty when the attacker has access to the application

When all the conditions above are met, the attacker can send malicious requests and poison the resource cache with resources using the wrong encoding. This can cause a denial of service by breaking the front-end application for clients.