CVSS v3.x: 6.1 (Medium)
- ~> 1.6.11
- >= 2.0.6
There is a possible vulnerability in Rack. This vulnerability has been assigned the CVE identifier CVE-2018-16471.
Versions Affected: All. Not affected: None. Fixed Versions: 2.0.6, 1.6.11
There is a possible XSS vulnerability in Rack. Carefully crafted requests can
impact the data returned by the
scheme method on
Applications that expect the scheme to be limited to "http" or "https" and do
not escape the return value could be vulnerable to an XSS attack.
Vulnerable code looks something like this:
<%= request.scheme.html_safe %>
Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.
All users running an affected release should either upgrade or use one of the workarounds immediately.
The 2.0.6 and 1.6.11 releases are available at the normal locations.
The following monkey patch can be applied to work around this issue:
require "rack" require "rack/request" class Rack::Request SCHEME_WHITELIST = %w(https http).freeze def scheme if get_header(Rack::HTTPS) == 'on' 'https' elsif get_header(HTTP_X_FORWARDED_SSL) == 'on' 'https' elsif forwarded_scheme forwarded_scheme else get_header(Rack::RACK_URL_SCHEME) end end def forwarded_scheme scheme_headers = [ get_header(HTTP_X_FORWARDED_SCHEME), get_header(HTTP_X_FORWARDED_PROTO).to_s.split(',') ] scheme_headers.each do |header| return header if SCHEME_WHITELIST.include?(header) end nil end end