NATS Server: `no_auth_user` pre-CONNECT fast path bypasses user connection restrictions

{
  "id": "20b3115c5cce5ed2d70ffe0e1aaab9c7953108f2cde540b04f59fedcadeae982",
  "url": "https://osv.dev/vulnerability/CVE-2026-58211",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "NATS Server: `no_auth_user` pre-CONNECT fast path bypasses user connection restrictions",
    "summary": "NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, a client could be registered as the configured no_auth_user through a parser path used when the first client operation was not CONNECT, bypassing user-level connection restrictions such as allowed_connection_types or proxy_required that normal authentication would apply. This issue is fixed in versions 2.14.3 and 2.12.12.",
    "evidence": "osv:CVE-2026-58211",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-58211",
      "aliases": [
        "CVE-2026-58211",
        "GHSA-hmmp-q8cx-v964"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nats-io/nats-server",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fc6ec648d806652d282d2f0edb6cb9f22c895572"
                },
                {
                  "fixed": "e8de2a67c7a094abca6013931ecf6cbff4b3fb02"
                },
                {
                  "introduced": "0cbd01caf8f29011c26273ff7662addd3830396a"
                },
                {
                  "fixed": "9b17a586be69c9ff36e4c84a421ca47da410b561"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.12.0"
                      },
                      {
                        "fixed": "2.12.12"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.14.0"
                      },
                      {
                        "fixed": "2.14.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.14.2",
            "v2.12.11",
            "v2.12.10",
            "v2.12.10-RC.1",
            "v2.14.2-RC.1",
            "v2.14.1",
            "v2.12.9",
            "v2.14.1-RC.2",
            "v2.12.9-RC.2",
            "v2.14.1-RC.1",
            "v2.12.9-RC.1",
            "v2.12.8",
            "v2.14.0",
            "v2.12.7",
            "v2.12.4",
            "v2.12.6",
            "v2.12.5",
            "v2.12.5-RC.2",
            "v2.12.5-RC.1",
            "v2.12.4-RC.6",
            "v2.12.4-RC.5",
            "v2.12.4-RC.4",
            "v2.12.2",
            "v2.12.4-RC.3",
            "v2.12.4-RC.2",
            "v2.12.4-RC.1",
            "v2.12.3",
            "v2.12.3-RC.5",
            "v2.12.3-RC.4",
            "v2.12.3-RC.3",
            "v2.12.3-RC.2",
            "v2.12.3-RC.1",
            "v2.12.2-RC.4",
            "v2.12.2-RC.3",
            "v2.12.1",
            "v2.12.2-RC.2",
            "v2.12.2-RC.1",
            "v2.12.0",
            "v2.12.1-RC.5",
            "v2.12.1-RC.4",
            "v2.12.1-RC.3",
            "v2.12.1-RC.2",
            "v2.12.1-RC.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-58211.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.925047741Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/58xxx/CVE-2026-58211.json",
        "https://github.com/nats-io/nats-server/security/advisories/GHSA-hmmp-q8cx-v964",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-58211"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-863"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/58xxx/CVE-2026-58211.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-58211",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519541,
  "published_at": "2026-07-08T20:16:25.262+00:00"
}