WFLY-16353 shows that configuring elytron SSO makes the request Input Stream unavailable. The main reason is that SSO in elytron reads the parameters and therefore elytron web consumes the input stream. Aftar that operation the InputStream cannot be read by the app again.

In the WFLY-16353 reproducer resteasy/jax-rs tries to create the Form using the input stream and just reads -1 because it was already consumed/parsed by elytron-web. Nevertheless it works for FormParam because it reuses the params already parsed by elytron-web. This JIRA will manage the idea of restoring the input stream in elytron-web somehow.