CVE-2020-5247: Improper Neutralization of CRLF Sequences in HTTP Headers

In Puma (RubyGem), if an application using Puma allows untrusted input in a response header, an attacker can use newline characters (i.e. CR, LF or /r, /n) 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).