CVE-2026-58208: nats-server — Fix

Description

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 WebSocket listener could route requests for the MQTT-over-WebSocket path into MQTT handling even when MQTT was not configured, allowing an unauthenticated client with access to the WebSocket listener to reach uninitialized MQTT state and crash the server process. This issue is fixed in versions 2.14.3 and 2.12.12.

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CVSS v3.1 Score

6.8

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0059

Probability of exploitation

0.45%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-248 CWE-248

Affected Products

Vendor	Product	Versions
linuxfoundation	nats-server	2.12.0 — 2.12.12
linuxfoundation	nats-server	2.14.0 — 2.14.3

References

Advisories & Patches

https://github.com/nats-io/nats-server/commit/73b3dd9a5ea0fa7bf08b702338676355b29b5fb4 https://github.com/nats-io/nats-server/commit/837536b98b3a9280b993282155ff2bdd3ca38c30 https://github.com/nats-io/nats-server/security/advisories/GHSA-p957-7v2w-g93g

Other References

https://github.com/nats-io/nats-server/releases/tag/v2.12.12 https://github.com/nats-io/nats-server/releases/tag/v2.14.3

Frequently Asked Questions

What is CVE-2026-58208? +

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 WebSocket listener could route requests for the MQTT-over-WebSocket path into MQTT handling even when MQTT was not configured, allowing an unauthenticated client with access to the WebSocket listener to reach uninitialized MQTT state and crash the server process. This issue is fixed in versions 2.14.3 and 2.12.12. It has a CVSS v3.1 base score of 6.8 (MEDIUM).

How severe is CVE-2026-58208? +

CVE-2026-58208 has a CVSS v3.1 score of 6.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0059, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-58208? +

CVE-2026-58208 affects products from linuxfoundation, specifically: nats-server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-58208? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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