CVE-2026-58209: CWE-863: Incorrect Authorization in nats-io nats-server
NATS Server versions prior to 2.14.3 and 2.12.12 have an incorrect authorization vulnerability affecting MQTT retained message delivery and QoS1+ durable replay. These delivery paths did not consistently recheck the original topic against subscriber deny rules, potentially allowing delivery of messages that should have been blocked. This issue is fixed in versions 2.14.3 and 2.12.12.
AI Analysis
Technical Summary
CVE-2026-58209 is an authorization bypass vulnerability in nats-io nats-server affecting MQTT retained message delivery and QoS1+ durable replay. Before versions 2.14.3 and 2.12.12, the server failed to consistently recheck the concrete original topic against subscriber deny rules before sending MQTT PUBLISH messages. This could result in messages being delivered to subscribers despite deny rules configured to block those topics. The vulnerability is classified as CWE-863 (Incorrect Authorization).
Potential Impact
The vulnerability allows messages to be delivered to MQTT subscribers even if their subscription deny rules should prevent such delivery. This could lead to unauthorized message reception, potentially exposing sensitive information to unintended recipients. The CVSS score is 4.3 (medium severity), indicating limited impact primarily on confidentiality without affecting integrity or availability.
Mitigation Recommendations
This vulnerability is fixed in nats-server versions 2.14.3 and 2.12.12. Users should upgrade to at least one of these versions to remediate the issue. No other mitigation or temporary workaround is indicated.
CVE-2026-58209: CWE-863: Incorrect Authorization in nats-io nats-server
Description
NATS Server versions prior to 2.14.3 and 2.12.12 have an incorrect authorization vulnerability affecting MQTT retained message delivery and QoS1+ durable replay. These delivery paths did not consistently recheck the original topic against subscriber deny rules, potentially allowing delivery of messages that should have been blocked. 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 is an authorization bypass vulnerability in nats-io nats-server affecting MQTT retained message delivery and QoS1+ durable replay. Before versions 2.14.3 and 2.12.12, the server failed to consistently recheck the concrete original topic against subscriber deny rules before sending MQTT PUBLISH messages. This could result in messages being delivered to subscribers despite deny rules configured to block those topics. The vulnerability is classified as CWE-863 (Incorrect Authorization).
Potential Impact
The vulnerability allows messages to be delivered to MQTT subscribers even if their subscription deny rules should prevent such delivery. This could lead to unauthorized message reception, potentially exposing sensitive information to unintended recipients. The CVSS score is 4.3 (medium severity), indicating limited impact primarily on confidentiality without affecting integrity or availability.
Mitigation Recommendations
This vulnerability is fixed in nats-server versions 2.14.3 and 2.12.12. Users should upgrade to at least one of these versions to remediate the issue. No other mitigation or temporary workaround 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: 07/08/2026, 20:29:20 UTC
Last updated: 07/09/2026, 01:52:07 UTC
Views: 4
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