js-yaml: Quadratic-complexity DoS in merge key handling via repeated aliases_CVE-2026-53550

{
    "lastseen": "",
    "description": "js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0.",
    "published": "2026-06-22T14:59:14.906Z",
    "modified": "2026-06-22T14:59:14.906Z",
    "type": "cve",
    "title": "js-yaml: Quadratic-complexity DoS in merge key handling via repeated aliases",
    "source": "GitHub_M",
    "references": "https://github.com/nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68",
    "id": "CVE-2026-53550",
    "bulletinFamily": "",
    "cwe": [
        "CWE-407"
    ],
    "cvelist": null,
    "sourceData": "nodeca js-yaml < 4.2.0",
    "sourceHref": "",
    "cvss": {
        "score": 5.3,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
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        "baseScore": 0,
        "baseSeverity": "",
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        "attackComplexity": "",
        "privilegesRequired": "",
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        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "js-yaml",
    "version": "< 4.2.0",
    "vendor": "nodeca",
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    "ai_score": 0
}