HTTP Response Splitting Affecting puma package, versions <3.12.4 >=4.0.0, <4.3.3



    Attack Complexity Low
Expand this section
6.5 medium
Expand this section
6.5 medium

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  • Snyk ID SNYK-RUBY-PUMA-559100
  • published 2 Mar 2020
  • disclosed 2 Mar 2020
  • credit Unknown

How to fix?

Upgrade puma to version 3.12.4, 4.3.3 or higher.


puma is a simple, fast, threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications. Puma is intended for use in both development and production environments. It's great for highly concurrent Ruby implementations such as Rubinius and JRuby as well as as providing process worker support to support CRuby well. Affected versions of this package are vulnerable to HTTP Response Splitting. If an application using Puma allows untrusted input in an early-hints header, an attacker can use a carriage return character to end the header and inject malicious content, such as additional headers or an entirely new response body. While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS).

Note: This is related to CVE-2020-5247, which fixed this vulnerability but only for regular responses.