{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "2.2.0"
              },
              {
                "fixed": "2.11.14"
              }
            ]
          },
          "events": [
            {
              "introduced": "0e3c7230e4b7c85795592f74a62351f6fe22fcbd"
            },
            {
              "fixed": "797d2514fdb29ccb2b654f7fefbcb166ccb66cf1"
            }
          ],
          "repo": "https://github.com/nats-io/nats-server",
          "type": "GIT"
        },
        {
          "database_specific": {
            "versions": [
              {
                "introduced": "2.12.0"
              },
              {
                "fixed": "2.12.5"
              }
            ]
          },
          "events": [
            {
              "introduced": "fc6ec648d806652d282d2f0edb6cb9f22c895572"
            },
            {
              "fixed": "0f6c831ec1df25bc3dc81d25faae0ed0bac15a96"
            }
          ],
          "repo": "https://github.com/nats-io/nats-server",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-pq2q-rcw4-3hr6"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-190"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27889.json"
  },
  "details": "NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server.  This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.",
  "id": "CVE-2026-27889",
  "modified": "2026-04-01T23:07:44.701028299Z",
  "published": "2026-03-25T19:36:36.370Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://advisories.nats.io/CVE/secnote-2026-03.txt"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27889.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27889"
    }
  ],
  "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:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead"
}