What is CVE-2026-58209?

CVE-2026-58209 is a medium-severity vulnerability in Nats-io Nats-server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-07-08.

How severe is CVE-2026-58209?

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

Auth bypass in Nats-io Nats-server

CVE-2026-58209

NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, MQTT retained message delivery and QoS1+ durable replay could deliver messages whose original topics matched a s…

Vulnerability class: Broken Access Control

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:L/I:N/A:N.

Affected products

Nats-io Nats-server — versions < 2.12.12, >= 2.14.0-RC.1, < 2.14.3

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-58209?: CVE-2026-58209 is a medium-severity vulnerability in Nats-io Nats-server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-07-08.
How severe is CVE-2026-58209?: Medium severity. CVSS v3 base score is 4.3 out of 10.