CVE-2026-58208CWE-248

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

Medium · published July 8, 2026

CVSS v3.1
6.8
EPSS
1%
Percentile
48.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
6.8 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00600 · 48.0th percentile
Weakness
CWE-248 · Uncaught Exception
Published
2026-07-08T20:17Z
EPSS history
Timeline
  • 08 JUL 20:17Z
    NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-Only JetStream Servers Before MQTT Is Enabled
    cvelistv5