{"schema_version":"1.7.5","id":"GHSA-8r68-gvr4-jh7j","published":"2026-03-24T21:46:31Z","modified":"2026-04-02T13:29:25.597966093Z","aliases":["BIT-nats-2026-33219","CVE-2026-33219","GO-2026-4831"],"related":["CGA-jmwc-c8gg-j9hp","CVE-2026-33219"],"summary":"NATS  is vulnerable to pre-auth DoS through WebSockets client service","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.","affected":[{"package":{"name":"github.com/nats-io/nats-server/v2","ecosystem":"Go","purl":"pkg:golang/github.com/nats-io/nats-server/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.11.15"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-8r68-gvr4-jh7j/GHSA-8r68-gvr4-jh7j.json"}},{"package":{"name":"github.com/nats-io/nats-server/v2","ecosystem":"Go","purl":"pkg:golang/github.com/nats-io/nats-server/v2"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.12.0-RC.1"},{"fixed":"2.12.6"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-8r68-gvr4-jh7j/GHSA-8r68-gvr4-jh7j.json"}},{"package":{"name":"github.com/nats-io/nats-server","ecosystem":"Go","purl":"pkg:golang/github.com/nats-io/nats-server"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-8r68-gvr4-jh7j/GHSA-8r68-gvr4-jh7j.json"}}],"references":[{"type":"WEB","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"},{"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"}],"database_specific":{"cwe_ids":["CWE-770"],"github_reviewed":true,"github_reviewed_at":"2026-03-24T21:46:31Z","nvd_published_at":"2026-03-25T20:16:32Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}