What is CVE-2026-33223?

CVE-2026-33223 is a medium-severity vulnerability in Nats-io Nats-server, classified under Authentication Bypass by Spoofing. CVSS score: 6.4/10. Published 2026-03-25.

How severe is CVE-2026-33223?

Medium severity. CVSS v3 base score is 6.4 out of 10.

Vulnerability in Nats-io Nats-server

CVE-2026-33223

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, the NATS message header `Nats-Request-Info:` is supposed to be a guarantee of identity by the NATS server…

EPSS: 0.000 (1.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N.

Affected products

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

Weakness classification (CWE)

CWE-290 — Authentication Bypass by Spoofing

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-pwx7-fx9r-hr4h (x_refsource_CONFIRM)
https://advisories.nats.io/CVE/secnote-2026-09.txt (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-33223?: CVE-2026-33223 is a medium-severity vulnerability in Nats-io Nats-server, classified under Authentication Bypass by Spoofing. CVSS score: 6.4/10. Published 2026-03-25.
How severe is CVE-2026-33223?: Medium severity. CVSS v3 base score is 6.4 out of 10.