Login Request a demo
High severity · published Jul 8, 2026
CVE-2026-58208
NATS Server: MQTT-over-WebSocket Path Can Crash WebSocket-Only JetStream Servers Before MQTT Is Enabled
7.5
CVSS
0.6%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 49% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NA
nats-server · nats-io
>= 2.14.0-RC.1, < 2.14.3; < 2.12.12 · source: vendor, NVD
Affected product
NA
nats-server
nats-io
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-58208
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-58208
Patch
https://github.com/nats-io/nats-server/commit/73b3dd9a5ea0fa7bf08b702338676355b29b5fb4
Patch
https://github.com/nats-io/nats-server/commit/837536b98b3a9280b993282155ff2bdd3ca38c30
Release Notes
https://github.com/nats-io/nats-server/releases/tag/v2.12.12
Release Notes
https://github.com/nats-io/nats-server/releases/tag/v2.14.3
Mitigation
https://github.com/nats-io/nats-server/security/advisories/GHSA-p957-7v2w-g93g
More from nats-server
8.8
CVE-2026-58253
NATS Server: Route API Auth Bypass
7.5
CVE-2026-58210
NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory
7.5
CVE-2026-58250
NATS Server: Pre-auth server crash via double INFO in leafnode handshake
7.1
CVE-2026-58213
NATS Server: MQTT SUBSCRIBE Protocol Injection via Leaf Node/Route Forwarding allows arbitrary NATS command injection
6.5
CVE-2026-58207
NATS Server: Remote crash via integer overflow in Connz pagination