What’s Vulnerable › Vulnerabilities
CVE-2026-32762: Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
- Severity: medium (CVSS 6.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-02 · updated 2026-07-24
- Weakness: CWE-436
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.
Affected products
- rack: from 3.0.0 before 3.1.21; from 3.2.0 before 3.2.6 — fixed in 3.1.21, 3.2.6
How to fix
Upgrade to a fixed version: rack 3.1.21, 3.2.6. Check the vendor advisory for mitigations.
References
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