Is CVE-2026-58211 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-58211 being exploited in the wild.

How severe is CVE-2026-58211?

Medium severity, with a CVSS score of 5.4, published 8 July 2026.

Which products and versions are affected?

nats-io NATS Server = 2.14.0-RC.1, < 2.14.3.

Is there a fix for CVE-2026-58211?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

How is CVE-2026-58211 attacked?

It is attacked over the network, in a hosted service.

Am I affected by CVE-2026-58211?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-58211: NATS Server authorization bypass in no_auth_user parser path

Q: Is there a fix for CVE-2026-58211?

No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

Q: How is CVE-2026-58211 attacked?

It is attacked over the network, in a hosted service.

Q: Am I affected by CVE-2026-58211?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-58211 · Severity: medium · CVSS 5.4 · Published 2026-07-08

NATS Server is a high-performance messaging system used for cloud and edge computing. A security flaw allows certain users to bypass connection restrictions, such as requirements to use a specific proxy or connection type. This could allow an unauthorized user to gain the permissions of a default 'no-authentication' user, potentially leading to unauthorized data access or message manipulation depending on that user's configuration.

Quick answers

Is CVE-2026-58211 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-58211 being exploited in the wild.
How severe is CVE-2026-58211?: Medium severity, with a CVSS score of 5.4, published 8 July 2026.
Which products and versions are affected?: nats-io NATS Server < 2.12.12, >= 2.14.0-RC.1, < 2.14.3.
Is there a fix for CVE-2026-58211?: No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-58211 attacked?: It is attacked over the network, in a hosted service.
Am I affected by CVE-2026-58211?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An incorrect authorization vulnerability (CWE-863) exists in NATS Server's parser logic. When a client's first operation is not a 'CONNECT' command, the server utilizes a specific parser path that registers the client as the configured 'no_auth_user' without enforcing standard connection restrictions like 'allowed_connection_types' or 'proxy_required'. An attacker with network access can exploit this to assume the identity and permissions of the default unauthenticated user while bypassing security boundaries intended to restrict that user to specific network paths or proxies. The issue is resolved in versions 2.14.3 and 2.12.12.

Affected products

nats-io NATS Server < 2.12.12, >= 2.14.0-RC.1, < 2.14.3

Timeline

2026-06-29: advisory: GitHub advisory published by maintainers
2026-07-08: disclosed: CVE published to NVD

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-hmmp-q8cx-v964

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