CVE-2020-5247

In Puma (RubyGem) before 4.3.2 and before 3.12.3, 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). This is related to
CVE-2019-16254, which fixed this vulnerability for the WEBrick Ruby web
server. This has been fixed in versions 4.3.2 and 3.12.3 by checking all
headers for line endings and rejecting headers with those characters.

Bugs

• <http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=952766&gt;