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

Quick assessment

Affected
rack rack
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Rack是Rack开源的一个模块化的Ruby web服务器界面。 Rack 3.0.0.beta1至3.1.21之前版本和3.2.0至3.2.6之前版本存在安全漏洞，该漏洞源于Forwarded标头解析不当，可能导致参数走私。

CVSS 4.8 · Medium EPSS 0.24% · P14

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-32762

Vulnerability Information
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Vulnerability Title
Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
解释冲突
Source: CVE Program / CVE List V5
Vulnerability Title
Rack 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Rack是Rack开源的一个模块化的Ruby web服务器界面。 Rack 3.0.0.beta1至3.1.21之前版本和3.2.0至3.2.6之前版本存在安全漏洞，该漏洞源于Forwarded标头解析不当，可能导致参数走私。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
rack rack >= 3.0.0.beta1, < 3.1.21 -

II. Public POCs for CVE-2026-32762

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III. Intelligence Information for CVE-2026-32762

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Vendor Advisories for CVE-2026-32762 (1)

Same Patch Batch · rack · 2026-04-02 · 13 CVEs total

CVE-2026-34785 7.5 HIGH Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching
CVE-2026-34827 7.5 HIGH Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser
CVE-2026-34829 7.5 HIGH Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length
CVE-2026-34830 5.9 MEDIUM Rack: Rack::Sendfile regex injection via HTTP_X_ACCEL_MAPPING header allows arbitrary file
CVE-2026-34826 5.3 MEDIUM Rack: Unbounded Range Count in get_byte_ranges Enables DoS
CVE-2026-34786 5.3 MEDIUM Rack: Rack::Static header_rules bypass via URL-encoded paths
CVE-2026-34763 5.3 MEDIUM Rack: Rack::Directory info disclosure and DoS via unescaped regex interpolation
CVE-2026-34230 5.3 MEDIUM Rack: Quadratic complexity in Rack::Utils.select_best_encoding via wildcard Accept-Encodin
CVE-2026-26962 4.8 MEDIUM Rack: Header injection in multipart requests
CVE-2026-34835 4.8 MEDIUM Rack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.
CVE-2026-34831 4.8 MEDIUM Rack: Content-Length mismatch in Rack::Files error responses
CVE-2026-26961 3.7 LOW Rack: Multipart Boundary Parsing Ambiguity allowing WAF Bypass

IV. Related Vulnerabilities

Same product: rack
Same vendor: rack
Same weakness: CWE-436

V. Comments for CVE-2026-32762

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