{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/nats-io/nats-server/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.11.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/nats-io/nats-server/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.12.0-RC.1"
            },
            {
              "fixed": "2.12.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33219"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-24T21:46:31Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Background\n\nNATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.\n\nThe nats-server offers a WebSockets client service, used in deployments where browsers are the NATS clients.\n\n### Problem Description\n\nA 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.\n\nThis is a milder variant of [NATS-advisory-ID 2026-02](https://advisories.nats.io/CVE/secnote-2026-02.txt) (aka CVE-2026-27571; GHSA-qrvq-68c2-7grw).\nThat earlier issue was a compression bomb, this vulnerability is not. Attacks against this new issue thus require significant client bandwidth.\n\n### Affected Versions\n\nAny version before v2.12.6 or v2.11.15\n\n### Workarounds\n\nDisable websockets if not required for project deployment.",
  "id": "GHSA-8r68-gvr4-jh7j",
  "modified": "2026-03-24T21:46:31Z",
  "published": "2026-03-24T21:46:31Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j"
    },
    {
      "type": "WEB",
      "url": "https://advisories.nats.io/CVE/secnote-2026-02.txt"
    },
    {
      "type": "WEB",
      "url": "https://advisories.nats.io/CVE/secnote-2026-11.txt"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-qrvq-68c2-7grw"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nats-io/nats-server"
    }
  ],
  "schema_version": "1.4.0",
  "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"
}