Rack ReDos in content type parsing (2nd degree polynomial)

Open Source Vulnerabilities CVE-2024-25126

Rack is a modular Ruby web server interface. Carefully crafted content type headers can cause Rack’s media type parser to take much longer than expected, leading to a possible denial of service vulnerability (ReDos 2nd degree polynomial). This vulnerability is patched in 3.0.9.1 and 2.2.8.1.

Open Source Vulnerabilities GHSA-22f2-v57c-j9cx

### Summary ```ruby module Rack class MediaType SPLIT_PATTERN = %r{\s*[;,]\s*} ``` The above regexp is subject to ReDos. 50K blank characters as a prefix to the header will take over 10s to split. ### PoC A simple HTTP request with lots of blank characters in the content-type header: ```ruby request["Content-Type"] = (" " * 50_000) + "a," ``` ### Impact It's a very easy to craft ReDoS. Like all ReDoS the impact is debatable.