HTTP Response Splitting vulnerability in puma

If an application using Puma allows untrusted input in a response header,
an attacker can use newline characters (i.e. CR, LF) to end the header and
inject malicious content, such as additional headers or an entirely new
response body. This vulnerability is known as HTTP Response Splitting.

While not an attack in itself, response splitting is a vector for several
other attacks, such as cross-site scripting (XSS).