CVE-2026-33219

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.

• CWE-770
• CWE-770

• https://advisories.nats.io/CVE/secnote-2026-02.txtMitigation, Vendor Advisory
• https://advisories.nats.io/CVE/secnote-2026-11.txtMitigation, Vendor Advisory
• https://github.com/advisories/GHSA-qrvq-68c2-7grwMitigation, Vendor Advisory
• https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7jMitigation, Vendor Advisory
• https://access.redhat.com/errata/RHSA-2026:21769
• https://access.redhat.com/errata/RHSA-2026:22347
• https://access.redhat.com/errata/RHSA-2026:23345
• https://access.redhat.com/security/cve/CVE-2026-33219
• https://bugzilla.redhat.com/show_bug.cgi?id=2451445
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33219.json

Published

Mar 25, 2026

Last Modified

Aug 10, 2026

Status

Modified

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