There is a possible DoS vulnerability in the multipart parser in Rack before 2.0.6. Specially crafted requests can cause the multipart parser to enter a pathological state, causing the parser to use CPU resources disproportionate to the request size.

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-16470
• https://access.redhat.com/errata/RHSA-2019:3172
• https://groups.google.com/forum/#!msg/rubyonrails-security/U_x-YkfuVTg/xhvYAmp6AAAJ
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/rack/CVE-2018-16470.yml
• https://groups.google.com/forum/#!topic/ruby-security-ann/Dz4sRl-ktKk