CVE-2026-32762: Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing

Rack::Utils.forwarded_values parses the RFC 7239 Forwarded header by splitting on semicolons before handling quoted-string values. Because quoted values may legally contain semicolons, a header such as:

Forwarded: for="127.0.0.1;host=evil.com;proto=https"

can be interpreted by Rack as multiple Forwarded directives rather than as a single quoted for value.

In deployments where an upstream proxy, WAF, or intermediary validates or preserves quoted Forwarded values differently, this discrepancy can allow an attacker to smuggle host, proto, for, or by parameters through a single header value.