CVE-2026-58208: CWE-248: Uncaught Exception in nats-io nats-server
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.
AI Analysis
Technical Summary
CVE-2026-58208 is a vulnerability in nats-io nats-server where a WebSocket listener improperly routes MQTT-over-WebSocket requests to MQTT handling even when MQTT is not enabled. This leads to an uncaught exception caused by accessing uninitialized MQTT state, resulting in a denial of service via server crash. The vulnerability affects versions prior to 2.12.12 and 2.14.3 and has a CVSS 3.1 base score of 6.8, indicating medium severity. No known exploits are reported in the wild. The issue is resolved in nats-server versions 2.12.12 and 2.14.3.
Potential Impact
An unauthenticated attacker with access to the WebSocket listener can cause the nats-server process to crash by triggering an uncaught exception related to uninitialized MQTT state. This results in a denial of service condition. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade nats-server to version 2.12.12 or 2.14.3 or later where this vulnerability is fixed. No other mitigations are indicated or necessary as the issue is resolved in these versions.
CVE-2026-58208: CWE-248: Uncaught Exception in nats-io nats-server
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 v3.1
Score 6.8medium
Affected software
pkg:github/nats-io/nats-serverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-58208 is a vulnerability in nats-io nats-server where a WebSocket listener improperly routes MQTT-over-WebSocket requests to MQTT handling even when MQTT is not enabled. This leads to an uncaught exception caused by accessing uninitialized MQTT state, resulting in a denial of service via server crash. The vulnerability affects versions prior to 2.12.12 and 2.14.3 and has a CVSS 3.1 base score of 6.8, indicating medium severity. No known exploits are reported in the wild. The issue is resolved in nats-server versions 2.12.12 and 2.14.3.
Potential Impact
An unauthenticated attacker with access to the WebSocket listener can cause the nats-server process to crash by triggering an uncaught exception related to uninitialized MQTT state. This results in a denial of service condition. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade nats-server to version 2.12.12 or 2.14.3 or later where this vulnerability is fixed. No other mitigations are indicated or necessary as the issue is resolved in these versions.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-29T17:09:25.872Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4eb691c9d9e3dbe3b68797
Added to database: 07/08/2026, 20:44:01 UTC
Last enriched: 07/16/2026, 10:12:21 UTC
Last updated: 08/22/2026, 10:52:10 UTC
Views: 133
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