CVE-2026-33217 HIGH

CVE-2026-33217: NATS allows MQTT clients to bypass ACL checks

Vendor Nats-Io
Product nats-server
Weakness CWE-863 · Incorrect authorization
Published March 25, 2026
Last update June 30, 2026
View on NVD All CVEs

CVSS base score

7.1/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality Low
Integrity High

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

March 25, 2026 CVE published
June 30, 2026 Record updated