It was reported that WildFly 10.0.0 Application Server/Undertow web server is vulnerable to the injection of arbitrary HTTP headers, and also Response Splitting, due to insufficient sanitisation and validation of user input before the input is used as part of a HTTP header value.

Using newline characters injected into the HTTP headers, it is possible for the malicious user to add arbitrary headers such as Set-Cookie to set arbitrary cookies, or potentially use a Location header for an open-redirect. By using two newline characters the attacker can 'split' the response (HTTP Response Splitting) and provide their own content that will be rendered to the victim user.