{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.11.15"
              }
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "bef17e1d9de6574fae0eabe1798db0d4529834e4"
            }
          ],
          "repo": "https://github.com/nats-io/nats-server",
          "type": "GIT"
        },
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "2.12.0-RC.1"
              },
              {
                "fixed": "2.12.6"
              }
            ]
          },
          "events": [
            {
              "introduced": "4dccf778573cd9a9e52fb8f119718459f6f2f761"
            },
            {
              "fixed": "0e0639058e0d2d8fce0cc34941f9897da152ab32"
            }
          ],
          "repo": "https://github.com/nats-io/nats-server",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-3f24-pcvm-5jqc"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-287",
      "CWE-295"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33248.json"
  },
  "details": "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.",
  "id": "CVE-2026-33248",
  "modified": "2026-04-01T23:08:40.060778362Z",
  "published": "2026-03-25T20:18:28.923Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://advisories.nats.io/CVE/secnote-2026-13.txt"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33248.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nats-io/nats-server/security/advisories/GHSA-3f24-pcvm-5jqc"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33248"
    }
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching"
}