NATS is vulnerable to pre-auth DoS through WebSockets client service_CVE-2026-33219

{
    "lastseen": "",
    "description": "NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, a malicious client which can connect to the WebSockets port can cause unbounded memory use in the nats-server before authentication; this requires sending a corresponding amount of data. This is a milder variant of CVE-2026-27571. That earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, disable websockets if not required for project deployment.",
    "published": "2026-03-25T19:55:28.363Z",
    "modified": "2026-03-25T20:10:35.721Z",
    "type": "cve",
    "title": "NATS is vulnerable to pre-auth DoS through WebSockets client service",
    "source": "GitHub_M",
    "references": "https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j\nhttps://advisories.nats.io/CVE/secnote-2026-02.txt\nhttps://advisories.nats.io/CVE/secnote-2026-11.txt\nhttps://github.com/advisories/GHSA-qrvq-68c2-7grw",
    "id": "CVE-2026-33219",
    "bulletinFamily": "",
    "cwe": [
        "CWE-770"
    ],
    "cvelist": null,
    "sourceData": "nats-io nats-server < 2.11.15\nnats-io nats-server >= 2.12.0-RC.1, < 2.12.6",
    "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": {
        "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": "nats-server",
    "version": "< 2.11.15",
    "vendor": "nats-io",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}