CVE-2026-33219

Name: CVE-2026-33219
Creator: NVD / NIST
Published: 2026-03-25T20:16:32.777+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.3/10EPSS 0.34%

Last modified Jun 17, 2026

CVE-2026-33219 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. 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. EPSS estimates a 0.34% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

5.3/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS Probability

0.34%

26.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-770

Affected Software

Vendor	Product	Versions
Linuxfoundation	Nats-Server	< 2.11.15
Linuxfoundation	Nats-Server	>= 2.12.0, < 2.12.6

References

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

Timeline

Published: Mar 25, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-33219?

How severe is CVE-2026-33219?

CVE-2026-33219 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.

How do I fix CVE-2026-33219?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-33219?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST