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

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Summary

CVECVE-2026-58208
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 21:16:52 UTC
Updated2026-07-09 19:08:52 UTC
DescriptionNATS 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.005930000 probability, percentile 0.442270000 (date 2026-07-11)

Problem Types: CWE-248 | CWE-248 CWE-248: Uncaught Exception

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
3.1CNADECLARED6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Linuxfoundation Nats-server All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Nats-io Nats-server affected >= 2.14.0-RC.1, < 2.14.3 Not specified
CNA Nats-io Nats-server affected < 2.12.12 Not specified

References

ReferenceSourceLinkTags
github.com/nats-io/nats-server/commit/73b3dd9a5ea0fa7bf08b702338676355b2... [email protected] github.com Patch
github.com/nats-io/nats-server/security/advisories/GHSA-p957-7v2w-g93g [email protected] github.com Mitigation, Vendor Advisory
github.com/nats-io/nats-server/releases/tag/v2.12.12 [email protected] github.com Release Notes
github.com/nats-io/nats-server/commit/837536b98b3a9280b993282155ff2bdd3c... [email protected] github.com Patch
github.com/nats-io/nats-server/releases/tag/v2.14.3 [email protected] github.com Release Notes
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