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CVE-2026-34831— Rack: Content-Length mismatch in Rack::Files error responses

CVSS 4.8 · Medium EPSS 0.04% · P13
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I. Basic Information for CVE-2026-34831

Vulnerability Information
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Vulnerability Title
Rack: Content-Length mismatch in Rack::Files error responses
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::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. 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:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
长度参数不一致性处理不恰当
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::Files#fail使用String#size而非String#bytesize设置Content-Length响应标头，可能导致HTTP响应帧错误。
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-2026-34831

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III. Intelligence Information for CVE-2026-34831

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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-2026-347865.3 MEDIUMRack: Rack::Static header_rules bypass via URL-encoded paths
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-2026-269613.7 LOWRack: Multipart Boundary Parsing Ambiguity allowing WAF Bypass

IV. Related Vulnerabilities

Same product: rack
Same vendor: rack
Same weakness: CWE-130

V. Comments for CVE-2026-34831

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