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CVE-2026-34786— Rack: Rack::Static header_rules bypass via URL-encoded paths

CVSS 5.3 · Medium EPSS 0.04% · P13
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I. Basic Information for CVE-2026-34786

Vulnerability Information
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Vulnerability Title
Rack: Rack::Static header_rules bypass via URL-encoded paths
Source: NVD (National Vulnerability Database)
Vulnerability Description
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
不正确的行为次序：规范化之前验证
Source: NVD (National Vulnerability Database)
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 2.2.23之前版本、3.1.21之前版本和3.2.6之前版本存在安全漏洞，该漏洞源于Rack::Static#applicable_rules针对原始URL编码的PATH_INFO评估标头规则，而底层文件服务路径在文件提供前已解码，可能导致攻击者绕过安全相关的响应标头。
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

VendorProductAffected VersionsCPESubscribe
rackrack < 2.2.23 -

II. Public POCs for CVE-2026-34786

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III. Intelligence Information for CVE-2026-34786

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

CVE-2026-347857.5 HIGHRack: Local file inclusion in `Rack::Static` via URL Prefix Matching
CVE-2026-348277.5 HIGHRack: Algorithmic-Complexity DoS in Rack::Multipart::Parser
CVE-2026-348297.5 HIGHRack: Denial of Service via Unbounded Multipart File Upload Without Content-Length
CVE-2026-348305.9 MEDIUMRack: Rack::Sendfile regex injection via HTTP_X_ACCEL_MAPPING header allows arbitrary file
CVE-2026-348265.3 MEDIUMRack: Unbounded Range Count in get_byte_ranges Enables DoS
CVE-2026-347635.3 MEDIUMRack: Rack::Directory info disclosure and DoS via unescaped regex interpolation
CVE-2026-342305.3 MEDIUMRack: Quadratic complexity in Rack::Utils.select_best_encoding via wildcard Accept-Encodin
CVE-2026-269624.8 MEDIUMRack: Header injection in multipart requests
CVE-2026-327624.8 MEDIUMRack: Forwarded Header semicolon injection enables Host and Scheme spoofing
CVE-2026-348354.8 MEDIUMRack: `Rack::Request` accepts invalid Host characters, enabling host allowlist bypass.
CVE-2026-348314.8 MEDIUMRack: Content-Length mismatch in Rack::Files error responses
CVE-2026-269613.7 LOWRack: Multipart Boundary Parsing Ambiguity allowing WAF Bypass

IV. Related Vulnerabilities

Same product: rack
Same vendor: rack
Same weakness: CWE-180

V. Comments for CVE-2026-34786

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