Inefficient Regular Expression Complexity

Summary

A denial of service vulnerability in the multipart parsing component of Rack versions 2.0.x prior to 2.0.9.2, 2.1.x prior to 2.1.4.2, 2.2.x prior to 2.2.6.1, and 3.0.x prior to 3.0.4.1 could allow an attacker to craft input that can cause RFC2183 multipart boundary parsing in Rack to take an unexpected amount of time, possibly resulting in a denial of service attack vector. Any applications that parse multipart posts using Rack (virtually all Rails applications) are impacted.