Medium 5.3Published Mar 25, 2026

CVE-2026-33219NATS is vulnerable to pre-auth DoS through WebSockets client service

Updated under an hour ago (Oct 27, 2026, 11:40 AM ET)

Does this affect you?

It affects nats-io nats-server and 3 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for nats-io nats-server

Exploited in the last 30 days

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: 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness (CWE): CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Modified
Record last updated: Sep 9, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

nats-io nats-server nats_io:nats_server (from the name)	before 2.11.15; from 2.12.0-RC.1, < 2.12.6	CNA record
Red Hat Multicluster Global Hub 1.4.5 redhat:multicluster_globalhub	from 1779579439 not affected	CISA ADP
Red Hat Red Hat OpenShift Container Platform 4 redhat:openshift	4	CISA ADP
linuxfoundation nats-server linuxfoundation:nats-server	before 2.11.15; from 2.12.0 before 2.12.6	NVD

References

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-8r68-gvr4-jh7j	x-refsource-confirm, mitigation, vendor-advisory
https://advisories.nats.io/CVE/secnote-2026-02.txt	x-refsource-misc, mitigation, vendor-advisory
https://advisories.nats.io/CVE/secnote-2026-11.txt	x-refsource-misc, mitigation, vendor-advisory
https://github.com/advisories/GHSA-qrvq-68c2-7grw	x-refsource-misc, mitigation, 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

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.