Sinatra rack-protection versions 1.5.4 and 2.0.0.rc3 and earlier contains a timing attack vulnerability in the CSRF token checking that can result in signatures can be exposed. This attack appear to be exploitable via network connectivity to the ruby application. This vulnerability appears to have been fixed in 1.5.5 and 2.0.0.
access.redhat.com/errata/RHSA-2018:1060
github.com/rubysec/ruby-advisory-db/blob/master/gems/rack-protection/CVE-2018-1000119.yml
github.com/sinatra/rack-protection
github.com/sinatra/rack-protection/pull/98
github.com/sinatra/sinatra/commit/8aa6c42ef724f93ae309fb7c5668e19ad547eceb#commitcomment-27964109
nvd.nist.gov/vuln/detail/CVE-2018-1000119
www.debian.org/security/2018/dsa-4247