h2 allows HTTP Request Smuggling due to illegal characters in headers_CVE-2025-57804

{
    "lastseen": "",
    "description": "h2 is a pure-Python implementation of a HTTP/2 protocol stack. Prior to version 4.3.0, an HTTP/2 request splitting vulnerability allows attackers to perform request smuggling attacks by injecting CRLF characters into headers. This occurs when servers downgrade HTTP/2 requests to HTTP/1.1 without properly validating header names/values, enabling attackers to manipulate request boundaries and bypass security controls. This issue has been patched in version 4.3.0.",
    "published": "2025-08-25T21:04:52.642Z",
    "modified": "2025-08-25T21:04:52.642Z",
    "type": "cve",
    "title": "h2 allows HTTP Request Smuggling due to illegal characters in headers",
    "source": "GitHub_M",
    "references": "https://github.com/python-hyper/h2/security/advisories/GHSA-847f-9342-265h\nhttps://github.com/python-hyper/h2/commit/035e9899f95e3709af098f578bfc3cd302298e3a",
    "id": "CVE-2025-57804",
    "bulletinFamily": "",
    "cwe": [
        "CWE-93"
    ],
    "cvelist": null,
    "sourceData": "python-hyper h2 < 4.3.0",
    "sourceHref": "",
    "cvss": {
        "score": 6.9,
        "severity": "MEDIUM",
        "vector": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
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        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "h2",
    "version": "< 4.3.0",
    "vendor": "python-hyper",
    "ai_description": "",
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    "ai_score": 0
}