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.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-qfgr-crr9-7r49 Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
Fixes

Solution

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Workaround

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History

Thu, 02 Apr 2026 20:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
Weaknesses CWE-436
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-02T17:42:42.305Z

Reserved: 2026-03-13T18:53:03.533Z

Link: CVE-2026-32762

cve-icon Vulnrichment

Updated: 2026-04-02T17:42:37.595Z

cve-icon NVD

Status : Received

Published: 2026-04-02T18:16:27.730

Modified: 2026-04-02T18:16:27.730

Link: CVE-2026-32762

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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Weaknesses