NATS-Server <=2.11.15 & 2.12.0-2.12.6: ACL bypass in $MQTT.>
CVE-2026-33217 Published on March 25, 2026

NATS allows MQTT clients to bypass ACL checks
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, when using ACLs on message subjects, these ACLs were not applied in the `$MQTT.>` namespace, allowing MQTT clients to bypass ACL checks for MQTT subjects. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.

NVD

Vulnerability Analysis

CVE-2026-33217 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
NONE

Weakness Types

What is an AuthZ Vulnerability?

The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

CVE-2026-33217 has been classified to as an AuthZ vulnerability or weakness.

What is a forced browsing Vulnerability?

The web application does not adequately enforce appropriate authorization on all restricted URLs, scripts, or files. Web applications susceptible to direct request attacks often make the false assumption that such resources can only be reached through a given navigation path and so only apply authorization at certain points in the path.

CVE-2026-33217 has been classified to as a forced browsing vulnerability or weakness.


Products Associated with CVE-2026-33217

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Red Hat Multicluster Globalhub
 
Red Hat Openshift
 

Affected Versions

nats-io nats-server: Red Hat Multicluster Global Hub 1.4.5: Red Hat Multicluster Global Hub 1.5.4: Red Hat Multicluster Global Hub 1.6.2: Red Hat OpenShift Container Platform 4:

Exploit Probability

EPSS
0.15%
Percentile
4.71%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.