fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names_CVE-2026-25896

{
    "lastseen": "",
    "description": "fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. From 4.1.3to before 5.3.5, a dot (.) in a DOCTYPE entity name is treated as a regex wildcard during entity replacement, allowing an attacker to shadow built-in XML entities (<, >, &, ", &apos;) with arbitrary values. This bypasses entity encoding and leads to XSS when parsed output is rendered. This vulnerability is fixed in 5.3.5.",
    "published": "2026-02-20T20:57:48.074Z",
    "modified": "2026-02-20T20:57:48.074Z",
    "type": "cve",
    "title": "fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names",
    "source": "GitHub_M",
    "references": "https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-m7jm-9gc2-mpf2\nhttps://github.com/NaturalIntelligence/fast-xml-parser/commit/943ef0eb1b2d3284e72dd74f44a042ee9f07026e\nhttps://github.com/NaturalIntelligence/fast-xml-parser/commit/ddcd0acf26ddd682cb0dc15a2bd6aa3b96bb1e69\nhttps://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.5",
    "id": "CVE-2026-25896",
    "bulletinFamily": "",
    "cwe": [
        "CWE-185"
    ],
    "cvelist": null,
    "sourceData": "NaturalIntelligence fast-xml-parser >= 4.1.3, < 5.3.5",
    "sourceHref": "",
    "cvss": {
        "score": 9.3,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/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": "",
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            "privilegesRequired": "",
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            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "fast-xml-parser",
    "version": ">= 4.1.3, < 5.3.5",
    "vendor": "NaturalIntelligence",
    "ai_description": "Entity encoding bypass via regex injection in DOCTYPE entity names, leading to XSS when parsed output is rendered",
    "ai_severity": "Critical",
    "ai_vendor": "NaturalIntelligence",
    "ai_product": "fast-xml-parser",
    "ai_version": "4.1.3 to 5.3.5",
    "ai_score": 9.3
}