NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching_CVE-2026-33248

{
    "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, when using mTLS for client identity, with `verify_and_map` to derive a NATS identity from the client certificate's Subject DN, certain patterns of RDN would not be correctly enforced, allowing for authentication bypass. This does require a valid certificate from a CA already trusted for client certificates, and `DN` naming patterns which the NATS maintainers consider highly unlikely. So this is an unlikely attack. Nonetheless, administrators who have been very sophisticated in their `DN` construction patterns might conceivably be impacted. Versions 2.11.15 and 2.12.6 contain a fix. As a workaround, developers should review their CA issuing practices.",
    "published": "2026-03-25T20:18:28.923Z",
    "modified": "2026-03-26T19:52:12.357Z",
    "type": "cve",
    "title": "NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching",
    "source": "GitHub_M",
    "references": "https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc\nhttps://advisories.nats.io/CVE/secnote-2026-13.txt",
    "id": "CVE-2026-33248",
    "bulletinFamily": "",
    "cwe": [
        "CWE-287",
        "CWE-295"
    ],
    "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": 4.2,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/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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            "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
}