What is CVE-2026-33249?

CVE-2026-33249 is a medium-severity vulnerability in Nats-io Nats-server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-03-25.

How severe is CVE-2026-33249?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Auth bypass in Nats-io Nats-server

CVE-2026-33249

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.11.0 and prior to versions 2.11.15 and 2.12.6, a valid client which uses message tracing headers can indicate that the tr…

Vulnerability class: Broken Access Control

EPSS: 0.000 (1.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.

Affected products

Nats-io Nats-server — versions >= 2.11.0, < 2.11.15, >= 2.12.0-preview.1, < 2.12.6

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-8m2x-3m6q-6w8j (x_refsource_CONFIRM)
https://advisories.nats.io/CVE/secnote-2026-15.txt (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-33249?: CVE-2026-33249 is a medium-severity vulnerability in Nats-io Nats-server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-03-25.
How severe is CVE-2026-33249?: Medium severity. CVSS v3 base score is 4.3 out of 10.