CVE-2026-32762
MediumCVSS 4.8Exploitation Probability (EPSS)
Low risk8th percentile - higher than 8% of all known CVEs
Summary
Rack before versions 3.1.21 and 3.2.6 incorrectly parses the Forwarded header (RFC 7239) by splitting on semicolons before handling quoted-string values. Since quoted values may contain semicolons, the header can be interpreted as multiple Forwarded directives, allowing attackers to smuggle host, proto, for, or by parameters.
Risk Assessment
Attackers can bypass proxy or WAF protections, potentially leading to host or protocol spoofing, and subsequent phishing or session hijacking attacks.
Recommendation
Update Rack to version 3.1.21, 3.2.6, or later.
Original NVD description (English source)
Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21 and 3.2.0 to before 3.2.6, 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 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. This issue has been patched in versions 3.1.21 and 3.2.6.