Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser_CVE-2026-34827

{
    "lastseen": "",
    "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::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name=\"...\" using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.",
    "published": "2026-04-02T17:07:48.279Z",
    "modified": "2026-04-03T18:13:16.834Z",
    "type": "cve",
    "title": "Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser",
    "source": "GitHub_M",
    "references": "https://github.com/rack/rack/security/advisories/GHSA-v6x5-cg8r-vv6x",
    "id": "CVE-2026-34827",
    "bulletinFamily": "",
    "cwe": [
        "CWE-407",
        "CWE-400",
        "CWE-770"
    ],
    "cvelist": null,
    "sourceData": "rack rack >= 3.0.0.beta1, < 3.1.21\nrack rack >= 3.2.0, < 3.2.6",
    "sourceHref": "",
    "cvss": {
        "score": 7.5,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "version": "3.1"
    },
    "cvss2": [],
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        "baseScore": 0,
        "baseSeverity": "",
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        "privilegesRequired": "",
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        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "rack",
    "version": ">= 3.0.0.beta1, < 3.1.21",
    "vendor": "rack",
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    "ai_score": 0
}