{
  "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"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-770"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33219.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, 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.",
  "id": "CVE-2026-33219",
  "modified": "2026-04-01T23:09:32.578294128Z",
  "published": "2026-03-25T19:55:28.363Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://advisories.nats.io/CVE/secnote-2026-02.txt"
    },
    {
      "type": "ADVISORY",
      "url": "https://advisories.nats.io/CVE/secnote-2026-11.txt"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33219.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-qrvq-68c2-7grw"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33219"
    }
  ],
  "related": [
    "GHSA-qrvq-68c2-7grw",
    "GHSA-8r68-gvr4-jh7j"
  ],
  "schema_version": "1.7.3",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "NATS is vulnerable to pre-auth DoS through WebSockets client service"
}