CVE-2026-33217 PUBLISHED

NATS allows MQTT clients to bypass ACL checks

Assigner: GitHub_M
Reserved: 17.03.2026 Published: 25.03.2026 Updated: 25.03.2026

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.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
CVSS Score: 7.1

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	Low	Integrity Impact	High
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	nats-io
Product	nats-server
Versions	Version < 2.11.15 is affected Version >= 2.12.0-RC.1, < 2.12.6 is affected

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-jxxm-27vp-c3m5
https://advisories.nats.io/CVE/secnote-2026-07.txt

Problem Types

CWE-863: Incorrect Authorization CWE