NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-Only JetStream Servers Before MQTT Is Enabled (nats-io nats-server)

CVE-2026-58208

MEDIUM 6.8

At a glance

Source: NVD
EPSS: EPSS 0.60 % · percentile 49 (2026-10-31)
State: PUBLISHED
Published: 2026-07-08 20:17 UTC
Updated: 2026-07-09 14:04 UTC
Assigner: GitHub_M
NVD status: Analyzed

Search on…

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.

Weaknesses (CWE)

CWE-248 — Uncaught Exception

References

Scores

Version	Score	Vector	Scored by
CVSS 3.1	MEDIUM 6.8	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H	GitHub_M
CVSS 3.1	MEDIUM 6.8	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H	NVD · security-advisories@github.com (Secondary)
CVSS 3.1	HIGH 7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	NVD · nvd@nist.gov (Primary)

European references

ENISA EUVD · EUVD-2026-42391
GCVE · GCVE-0-2026-58208

Affected configurations (NVD CPE)

cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:* ≥ 2.12.0 < 2.12.12
cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:* ≥ 2.14.0 < 2.14.3

Affected products

Product	Versions
nats-io · nats-server	affected >= 2.14.0-RC.1, < 2.14.3 ; affected < 2.12.12

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD

🟡 NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-Only JetStream Servers Before MQTT Is Enabled (nats-io nats-server)