# CVE-2026-58208: NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-Only JetStream Servers Before MQTT Is Enabled

CVE-2026-58208 is fixed in nats-server on 1 platform by DEBIAN-CVE-2026-58208 (version 2.14.3-1), released July 6, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-58208
- Priority: High
- CVSS: 7.5 (Moderate)
- EPSS: 0.0060
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 8, 2026
- Weakness: Uncaught Exception
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-58208

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | nats-server Debian 14 | 2.14.3-1 | [DEBIAN-CVE-2026-58208](https://patchblox.com/security/data/fix/linux/debian-cve-2026-58208.md) | Jul 6, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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