What is CVE-2026-33215?

CVE-2026-33215 is a medium-severity vulnerability in Nats-io Nats-server, classified under Improper Authentication. CVSS score: 6.5/10. Published 2026-03-24.

How severe is CVE-2026-33215?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Auth bypass in Nats-io Nats-server

CVE-2026-33215

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client…

Vulnerability class: Broken Authentication

EPSS: 0.000 (4.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L.

Affected products

Nats-io Nats-server — versions < 2.11.15, >= 2.12.0-RC.1, < 2.12.6

Weakness classification (CWE)

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-fcjp-h8cc-6879 (x_refsource_CONFIRM)
https://advisories.nats.io/CVE/secnote-2026-06.tx (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-33215?: CVE-2026-33215 is a medium-severity vulnerability in Nats-io Nats-server, classified under Improper Authentication. CVSS score: 6.5/10. Published 2026-03-24.
How severe is CVE-2026-33215?: Medium severity. CVSS v3 base score is 6.5 out of 10.