Tornado is Vulnerable to Quadratic DoS via Crafted Multipart Parameters_CVE-2025-67726

{
    "lastseen": "",
    "description": "Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted semicolons. If an attacker sends a request with a large number of maliciously crafted parameters in a Content-Disposition header, the server's CPU usage increases quadratically (O(n\u00b2)) during parsing. Due to Tornado's single event loop architecture, a single malicious request can cause the entire server to become unresponsive for an extended period. This issue is fixed in version 6.5.3.",
    "published": "2025-12-12T06:13:51.336Z",
    "modified": "2025-12-12T06:13:51.336Z",
    "type": "cve",
    "title": "Tornado is Vulnerable to Quadratic DoS via Crafted Multipart Parameters",
    "source": "GitHub_M",
    "references": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-jhmp-mqwm-3gq8\nhttps://github.com/tornadoweb/tornado/commit/771472cfdaeebc0d89a9cc46e249f8891a6b29cd\nhttps://github.com/tornadoweb/tornado/releases/tag/v6.5.3",
    "id": "CVE-2025-67726",
    "bulletinFamily": "",
    "cwe": [
        "CWE-834",
        "CWE-400"
    ],
    "cvelist": null,
    "sourceData": "tornadoweb tornado < 6.5.3",
    "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": [],
    "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": "tornado",
    "version": "< 6.5.3",
    "vendor": "tornadoweb",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}