TI-2026-41918 Aliases CVE-2026-58208

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

LOW 34CWE-248Published 2026-07-08 · Updated 2026-07-09

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-248.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.006 48th percentileScored 2026-11-07

Fix Fixed nats-server (nats-io): 2.14.3, 2.12.12

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
backstage	nats-server	2.14.0-RC.1 to before 2.14.3; before 2.12.12	2.14.3, 2.12.12	Patch available	CNA

nats-server Vendorbackstage Affected 2.14.0-RC.1 to before 2.14.3; before 2.12.12 Fixed in 2.14.3, 2.12.12 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:linuxfoundation:nats-server::::::::	2.12.0 to before 2.12.12; 2.14.0 to before 2.14.3	Vulnerable	backstage

cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:* Versions 2.12.0 to before 2.12.12; 2.14.0 to before 2.14.3 Vulnerable ·backstage

Remediation

Fix · CNA nats-server (nats-io) Fixed in 2.14.3, 2.12.12

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Not affected: 1 product

Red Hat Hardened Images

Timeline

2026-10-02 Threatist record created from CVE-2026-58208

References

Patch 2

Advisory 1

https://github.com/nats-io/nats-server/security/advisories/GHSA-p957-7v2w-g93g

Other 2

TI-2026-22233 NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead CVSS 3.1HIGH 7.5
TI-2022-11116 NATS nats-server 2.2.0 through 2.7.4 allows directory traversal because of an unintended… CVSS 3.1CRITICAL 9.8
TI-2020-16319 The JWT library in NATS nats-server before 2.1.9 has Incorrect Access Control because of… CVSS 3.1CRITICAL 9.8
TI-2026-25637 NATS has MQTT plaintext password disclosure CVSS 3.1HIGH 8.6
TI-2022-08320 NATS nats-server before 2.7.2 has Incorrect Access Control. CVSS 3.1HIGH 8.8
TI-2026-41950 NATS Server: Pre-auth server crash via double INFO in leafnode handshake CVSS 3.1HIGH 7.5

See all 35 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences