CVE-2026-58208mediumCWE-248

CVE-2026-58208: medium-severity vulnerability in nats-io nats-server

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

Published · Updated

Follow this CVE+ Monitor nats-server+ Monitor nats-server

E-mail alert when it lands in KEV, gets a public PoC or its score goes up.

13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.8epss 0.6%
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Affected products
nats-io · nats-server
Related CVEs — nats-io nats-server

In the same product, most dangerous first.

CVE-2026-58210HIGHNATS Server: MQTT partial CONNECT packets can exhaust pre-auth memoryEPSS 0.7%CVE-2026-58250HIGHNATS Server: Pre-auth server crash via double INFO in leafnode handshakeEPSS 0.7%CVE-2026-29785HIGHNATS Server panic via malicious compression on leafnode portEPSS 0.7%CVE-2026-33218HIGHNATS has pre-auth server panic via leafnode handlingEPSS 0.6%CVE-2025-30215CRITICALNATS-Server Fails to Authorize Certain Jetstream Admin APIsEPSS 0.6%CVE-2026-27889HIGHNATS: Pre-auth remote server crash via WebSocket frame length overflow in wsReadEPSS 0.6%