Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks_CVE-2026-48710

{
    "lastseen": "",
    "description": "Starlette is a lightweight ASGI framework/toolkit. Prior to version 1.0.1, the HTTP `Host` request header was not validated before being used to reconstruct `request.url`. Because the routing algorithm relies on the raw HTTP path while `request.url` is rebuilt from the `Host` header, a malformed header could make `request.url.path` differ from the path that was actually requested. Middleware and endpoints that apply security restrictions based on `request.url` (rather than the raw `scope` path) could therefore be bypassed. Users should upgrade to a version greater than or equal to version 1.0.1, which validates the `Host` header against the grammar of RFC 9112 \u00a73.2 / RFC 3986 \u00a73.2.2 when constructing `request.url` and falls back to `scope[\"server\"]` for malformed values.",
    "published": "2026-05-26T21:54:54.393Z",
    "modified": "2026-05-26T21:54:54.393Z",
    "type": "cve",
    "title": "Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks",
    "source": "GitHub_M",
    "references": "https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr\nhttps://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6\nhttps://badhost.org\nhttps://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml\nhttps://ostif.org/disclosing-the-badhost-vulnerability-in-starlette\nhttps://www.secwest.net/starlette\nhttps://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette",
    "id": "CVE-2026-48710",
    "bulletinFamily": "",
    "cwe": [
        "CWE-444"
    ],
    "cvelist": null,
    "sourceData": "Kludex starlette < 1.0.1",
    "sourceHref": "",
    "cvss": {
        "score": 6.5,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "starlette",
    "version": "< 1.0.1",
    "vendor": "Kludex",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}