jupyter-server CORS origin validation bypass via unanchored regex in allow_origin_pat_CVE-2026-40110

{
    "lastseen": "",
    "description": "Jupyter Server is the backend for Jupyter web applications. In versions 2.17.0 and earlier, the Origin header validation uses Python's re.match() to check incoming origins against the allow_origin_pat configuration value. Because re.match() only anchors at the start of the string and does not require a full match, a pattern intended to match only a trusted domain (e.g., trusted.example.com) will also match any origin that begins with that domain followed by additional characters (e.g., trusted.example.com.evil.com). An attacker who controls such a domain can bypass the CORS origin restriction and make cross-origin requests to the Jupyter Server API from an untrusted site. This issue has been fixed in version 2.18.0.",
    "published": "2026-05-05T21:29:31.323Z",
    "modified": "2026-05-05T21:29:31.323Z",
    "type": "cve",
    "title": "jupyter-server CORS origin validation bypass via unanchored regex in allow_origin_pat",
    "source": "GitHub_M",
    "references": "https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-24qx-w28j-9m6p\nhttps://github.com/jupyter-server/jupyter_server/pull/603\nhttps://github.com/jupyter-server/jupyter_server/commit/057869a327c46730afede3eab0ca2d2e3e74acea\nhttps://github.com/jupyter-server/jupyter_server/commit/49b34392feaa97735b3b777e3baf8f22f2a14ed8",
    "id": "CVE-2026-40110",
    "bulletinFamily": "",
    "cwe": [
        "CWE-777"
    ],
    "cvelist": null,
    "sourceData": "jupyter-server jupyter_server <= 2.17.0",
    "sourceHref": "",
    "cvss": {
        "score": 7.6,
        "severity": "HIGH",
        "vector": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:L/SC:L/SI:L/SA:L",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
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            "privilegesRequired": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "jupyter_server",
    "version": "<= 2.17.0",
    "vendor": "jupyter-server",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
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    "ai_score": 0
}