CVE-2026-58209: CWE-863: Incorrect Authorization 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, MQTT retained message delivery and QoS1+ durable replay could deliver messages whose original topics matched a subscriber configured subscribe deny rule because these delivery paths did not consistently recheck the concrete original topic before sending the MQTT PUBLISH to the subscriber. This issue is fixed in versions 2.14.3 and 2.12.12.
AI Analysis
Technical Summary
CVE-2026-58209 describes an incorrect authorization vulnerability (CWE-863) in nats-io nats-server affecting MQTT retained message delivery and QoS1+ durable replay. Prior to versions 2.14.3 and 2.12.12, the server failed to consistently revalidate the original topic against subscriber deny rules before sending MQTT PUBLISH messages. This could result in messages being delivered to subscribers even when their subscription rules should deny them. The vulnerability is fixed in nats-server versions 2.14.3 and 2.12.12.
Potential Impact
The vulnerability allows messages to be delivered to MQTT subscribers despite configured deny rules on their subscriptions. This could lead to unauthorized message reception, potentially exposing sensitive or restricted information to unintended recipients. The CVSS score of 4.3 indicates a medium severity impact with low complexity and no user interaction required. There is no indication of integrity or availability impact.
Mitigation Recommendations
Upgrade nats-server to version 2.14.3 or 2.12.12 or later, where the issue is fixed. Patch status is confirmed by the vendor advisory specifying these versions as fixed. No additional mitigation is indicated.
CVE-2026-58209: CWE-863: Incorrect Authorization 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, MQTT retained message delivery and QoS1+ durable replay could deliver messages whose original topics matched a subscriber configured subscribe deny rule because these delivery paths did not consistently recheck the concrete original topic before sending the MQTT PUBLISH to the subscriber. This issue is fixed in versions 2.14.3 and 2.12.12.
CVSS v3.1
Score 4.3medium
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-2026-58209 describes an incorrect authorization vulnerability (CWE-863) in nats-io nats-server affecting MQTT retained message delivery and QoS1+ durable replay. Prior to versions 2.14.3 and 2.12.12, the server failed to consistently revalidate the original topic against subscriber deny rules before sending MQTT PUBLISH messages. This could result in messages being delivered to subscribers even when their subscription rules should deny them. The vulnerability is fixed in nats-server versions 2.14.3 and 2.12.12.
Potential Impact
The vulnerability allows messages to be delivered to MQTT subscribers despite configured deny rules on their subscriptions. This could lead to unauthorized message reception, potentially exposing sensitive or restricted information to unintended recipients. The CVSS score of 4.3 indicates a medium severity impact with low complexity and no user interaction required. There is no indication of integrity or availability impact.
Mitigation Recommendations
Upgrade nats-server to version 2.14.3 or 2.12.12 or later, where the issue is fixed. Patch status is confirmed by the vendor advisory specifying these versions as fixed. No additional mitigation is indicated.
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: 6a4eafe7c9d9e3dbe3adea0a
Added to database: 07/08/2026, 20:15:35 UTC
Last enriched: 07/16/2026, 10:12:28 UTC
Last updated: 08/22/2026, 10:52:10 UTC
Views: 58
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