UBUNTU-CVE-2026-58209
NATS Server versions prior to 2.14.3 and 2.12.12 have a vulnerability where MQTT retained message delivery and QoS1+ durable replay can deliver messages to subscribers even if their subscribe deny rules should block those messages. This occurs because the delivery paths did not consistently recheck the original topic against the subscriber's deny rules before sending the MQTT PUBLISH message. The issue is resolved in versions 2.14.3 and 2.12.12.
AI Analysis
Technical Summary
The vulnerability in NATS Server affects MQTT message delivery mechanisms. Specifically, retained messages and QoS1+ durable replay could bypass subscriber subscribe deny rules by not properly revalidating the original topic before delivering the MQTT PUBLISH message. This could result in subscribers receiving messages they should have been denied. The flaw is fixed in NATS Server versions 2.14.3 and 2.12.12.
Potential Impact
Confidentiality impact is limited to the potential delivery of MQTT messages to subscribers that should have been blocked by subscribe deny rules. There is no impact on integrity or availability. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade affected NATS Server instances to version 2.14.3 or 2.12.12 or later, where the issue is fixed. No other mitigation is indicated or required.
UBUNTU-CVE-2026-58209
Description
NATS Server versions prior to 2.14.3 and 2.12.12 have a vulnerability where MQTT retained message delivery and QoS1+ durable replay can deliver messages to subscribers even if their subscribe deny rules should block those messages. This occurs because the delivery paths did not consistently recheck the original topic against the subscriber's deny rules before sending the MQTT PUBLISH message. The issue is resolved in versions 2.14.3 and 2.12.12.
CVSS v3.1
Score 4.3medium
Affected software
pkg:deb/ubuntu/[email protected]?arch=source&distro=noblepkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]~esm1?arch=source&distro=esm-apps/resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in NATS Server affects MQTT message delivery mechanisms. Specifically, retained messages and QoS1+ durable replay could bypass subscriber subscribe deny rules by not properly revalidating the original topic before delivering the MQTT PUBLISH message. This could result in subscribers receiving messages they should have been denied. The flaw is fixed in NATS Server versions 2.14.3 and 2.12.12.
Potential Impact
Confidentiality impact is limited to the potential delivery of MQTT messages to subscribers that should have been blocked by subscribe deny rules. There is no impact on integrity or availability. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade affected NATS Server instances to version 2.14.3 or 2.12.12 or later, where the issue is fixed. No other mitigation is indicated or required.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-58209
- Osv Schema Version
- 1.7.0
- Aliases
- []
- Ecosystems
- ["Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:Pro:26.04:LTS"]
- Database Specific Severity
- null
- Cvss Version
- 3.1
Threat ID: 6a58b46268715ace43d6e7fd
Added to database: 07/16/2026, 10:37:22 UTC
Last enriched: 07/16/2026, 11:37:11 UTC
Last updated: 07/31/2026, 19:24:47 UTC
Views: 6
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