What is CVE-2026-58211?

CVE-2026-58211 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-07-08.

How severe is CVE-2026-58211?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Auth bypass in Linuxfoundation Nats-Server

CVE-2026-58211

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, a client could be registered as the configured no_auth_user through a parser path used when the first client operation was not CONNECT, bypassing user-level connection restrictions such as allowed_connection_types or proxy_required that normal authentication would apply. This issue is fixed in versions 2.14.3 and 2.12.12.

Vulnerability class: Broken Access Control

EPSS: 0.002 (11.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.

Affected products

Linuxfoundation Nats-server
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_CONFIRM, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-58211?: CVE-2026-58211 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-07-08.
How severe is CVE-2026-58211?: Medium severity. CVSS v3 base score is 5.4 out of 10.