{"cve":"CVE-2026-33219","nvd":{"published":"2026-03-25T20:16:32.777","modified":"2026-09-09T13:19:24.173","status":"Modified","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-770"],"references":["https://advisories.nats.io/CVE/secnote-2026-02.txt","https://advisories.nats.io/CVE/secnote-2026-11.txt","https://github.com/advisories/GHSA-qrvq-68c2-7grw","https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j","https://access.redhat.com/errata/RHSA-2026:21769"],"products":["linuxfoundation:nats-server"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-33219","score":0.00546,"percentile":0.4579,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-8r68-gvr4-jh7j","url":"https://osv.dev/vulnerability/GHSA-8r68-gvr4-jh7j","summary":"NATS  is vulnerable to pre-auth DoS through WebSockets client service","modified":"2026-09-10T03:50:38.245297667Z","packages":[{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","purl":"pkg:golang/github.com/nats-io/nats-server/v2","ranges":["<2.11.15"],"fixed":["2.11.15"]},{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","purl":"pkg:golang/github.com/nats-io/nats-server/v2","ranges":[">=2.12.0-RC.1 <2.12.6"],"fixed":["2.12.6"]},{"ecosystem":"Go","name":"github.com/nats-io/nats-server","purl":"pkg:golang/github.com/nats-io/nats-server","ranges":["all versions"],"fixed":[]}]},{"id":"GO-2026-4831","url":"https://osv.dev/vulnerability/GO-2026-4831","summary":"NATS is vulnerable to pre-auth DoS through WebSockets client service in github.com/nats-io/nats-server","modified":"2026-03-27T18:26:09.072082Z","packages":[{"ecosystem":"Go","name":"github.com/nats-io/nats-server","purl":"pkg:golang/github.com/nats-io/nats-server","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","purl":"pkg:golang/github.com/nats-io/nats-server/v2","ranges":["<2.11.15",">=2.12.0-RC.1 <2.12.6"],"fixed":["2.11.15","2.12.6"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}