What is CVE-2026-33215?

CVE-2026-33215 is a medium-severity vulnerability in Linuxfoundation 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 Linuxfoundation 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 ID malfeasance. Versions 2.11.15 and 2.12.5 patch the issue. No known workarounds are available.

Vulnerability class: Broken Authentication

EPSS: 0.002 (15.0th 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

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

Weakness classification (CWE)

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
security-advisories@github.com (x_refsource_MISC, Broken Link)

Frequently asked questions

What is CVE-2026-33215?: CVE-2026-33215 is a medium-severity vulnerability in Linuxfoundation 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.