{"id":"CVE-2026-33219","summary":"NATS is vulnerable to pre-auth DoS through WebSockets client service","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.","aliases":["BIT-nats-2026-33219","GHSA-8r68-gvr4-jh7j","GO-2026-4831"],"modified":"2026-05-28T03:54:33.730198225Z","published":"2026-03-25T19:55:28.363Z","related":["CGA-jmwc-c8gg-j9hp","GHSA-8r68-gvr4-jh7j","GHSA-qrvq-68c2-7grw","SUSE-SU-2026:1135-1"],"database_specific":{"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33219.json","cwe_ids":["CWE-770"]},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nats-io/nats-server","events":[{"introduced":"4dccf778573cd9a9e52fb8f119718459f6f2f761"},{"fixed":"0e0639058e0d2d8fce0cc34941f9897da152ab32"}]}],"versions":["v2.12.4","v2.12.5","v2.12.5-RC.2","v2.12.5-RC.1","v2.12.4-RC.6","v2.12.4-RC.5","v2.12.4-RC.4","v2.12.2","v2.12.4-RC.3","v2.12.4-RC.2","v2.12.4-RC.1","v2.12.3","v2.12.3-RC.5","v2.12.3-RC.4","v2.12.3-RC.3","v2.12.3-RC.2","v2.12.3-RC.1","v2.12.2-RC.4","v2.12.2-RC.3","v2.12.1","v2.12.2-RC.2","v2.12.2-RC.1","v2.12.0","v2.12.1-RC.5","v2.12.1-RC.4","v2.12.1-RC.3","v2.12.1-RC.2","v2.12.1-RC.1","v2.12.0-RC.6","v2.12.0-RC.5","v2.12.0-RC.4","v2.12.0-RC.3","v2.12.0-RC.2","v2.12.0-RC.1"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-33219.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}