Werkzeug safe_join() allows Windows special device names_CVE-2026-27199

{
    "lastseen": "",
    "description": "Werkzeug is a comprehensive WSGI web application library. Versions 3.1.5 and below, the safe_join function allows Windows device names as filenames if preceded by other path segments. This was previously reported as GHSA-hgf8-39gv-g3f2, but the added filtering failed to account for the fact that safe_join accepts paths with multiple segments, such as example/NUL. The function send_from_directory uses safe_join to safely serve files at user-specified paths under a directory. If the application is running on Windows, and the requested path ends with a special device name, the file will be opened successfully, but reading will hang indefinitely. This issue has been fixed in version 3.1.6.",
    "published": "2026-02-21T05:15:53.335Z",
    "modified": "2026-02-21T05:15:53.335Z",
    "type": "cve",
    "title": "Werkzeug safe_join() allows Windows special device names",
    "source": "GitHub_M",
    "references": "https://github.com/pallets/werkzeug/security/advisories/GHSA-29vq-49wr-vm6x\nhttps://github.com/pallets/werkzeug/commit/f407712fdc60a09c2b3f4fe7db557703e5d9338d\nhttps://github.com/pallets/werkzeug/releases/tag/3.1.6",
    "id": "CVE-2026-27199",
    "bulletinFamily": "",
    "cwe": [
        "CWE-67"
    ],
    "cvelist": null,
    "sourceData": "pallets werkzeug < 3.1.6",
    "sourceHref": "",
    "cvss": {
        "score": 6.3,
        "severity": "MEDIUM",
        "vector": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
        "version": "4.0"
    },
    "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": "werkzeug",
    "version": "< 3.1.6",
    "vendor": "pallets",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}