NATS Server: MQTT subscribe ACL bypass via $MQTT.deliver.pubrel prefix (incomplete fix for CVE-2026-33217) (CVE-2026-58214)
NATS Server versions prior to 2.14.3 and 2.12.12 contain a vulnerability where an authenticated MQTT client can bypass subscribe access controls by subscribing to the internal $MQTT.deliver.pubrel subject prefix. This exposes MQTT QoS2 protocol metadata for sessions within the account. The issue is addressed in versions 2.14.3 and 2.12.12.
AI Analysis
Technical Summary
NATS Server, a messaging system server, had an incomplete fix for CVE-2026-33217 that allowed authenticated MQTT clients to bypass subscribe ACLs by subscribing to the internal subject family $MQTT.deliver.pubrel. This bypass exposes MQTT QoS2 protocol metadata for sessions in the account. The vulnerability affects versions before 2.12.12 and 2.14.3, where the issue is fixed.
Potential Impact
An authenticated MQTT client can bypass configured subscribe permissions, potentially exposing MQTT QoS2 protocol metadata related to sessions in the affected account. This could lead to unauthorized access to internal messaging protocol details, which may aid in further attacks or information disclosure within the account context.
Mitigation Recommendations
Upgrade NATS Server to version 2.14.3 or 2.12.12 or later, where this vulnerability is fixed. No other mitigation is indicated by the vendor advisory.
NATS Server: MQTT subscribe ACL bypass via $MQTT.deliver.pubrel prefix (incomplete fix for CVE-2026-33217) (CVE-2026-58214)
Description
NATS Server versions prior to 2.14.3 and 2.12.12 contain a vulnerability where an authenticated MQTT client can bypass subscribe access controls by subscribing to the internal $MQTT.deliver.pubrel subject prefix. This exposes MQTT QoS2 protocol metadata for sessions within the account. The issue is addressed in versions 2.14.3 and 2.12.12.
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
NATS Server, a messaging system server, had an incomplete fix for CVE-2026-33217 that allowed authenticated MQTT clients to bypass subscribe ACLs by subscribing to the internal subject family $MQTT.deliver.pubrel. This bypass exposes MQTT QoS2 protocol metadata for sessions in the account. The vulnerability affects versions before 2.12.12 and 2.14.3, where the issue is fixed.
Potential Impact
An authenticated MQTT client can bypass configured subscribe permissions, potentially exposing MQTT QoS2 protocol metadata related to sessions in the affected account. This could lead to unauthorized access to internal messaging protocol details, which may aid in further attacks or information disclosure within the account context.
Mitigation Recommendations
Upgrade NATS Server to version 2.14.3 or 2.12.12 or later, where this vulnerability is fixed. No other mitigation is indicated by the vendor advisory.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-58214
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:Pro:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a58b45d68715ace43d6be3a
Added to database: 07/16/2026, 10:37:17 UTC
Last enriched: 09/08/2026, 15:19:45 UTC
Last updated: 09/14/2026, 10:01:32 UTC
Views: 32
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