CVE-2026-33217
NATS allows MQTT clients to bypass ACL checks
6.5
MEDIUM
CVSS 3.1
EPSS 0.26%
Description
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.
How to fix CVE-2026-33217
To remediate CVE-2026-33217, upgrade the affected package to a fixed version below.
- —upgrade to 2.11.15 or later
Is CVE-2026-33217 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 2.11.15, >= 2.12.0, < 2.12.6
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |