Potential Bypass of ACLs in NATS-Server by MQTT Clients
CVE-2026-33217

7.1HIGH

Key Information:

Vendor

Nats-io

Status
Nats-server
Vendor
CVE Published:
25 March 2026

What is CVE-2026-33217?

NATS-Server, a high-performance messaging system for cloud and edge environments, faced a significant vulnerability in its ACL implementation. Specifically, prior to versions 2.11.15 and 2.12.6, Access Control Lists (ACLs) applied to message subjects were not enforced within the $MQTT.> namespace, enabling MQTT clients to bypass essential ACL checks. This oversight could result in unauthorized message access. The affected versions have been updated to address this critical issue, and no known workarounds exist for users relying on the compromised functionality.

Affected Version(s)

nats-server < 2.11.15 < 2.11.15

nats-server >= 2.12.0-RC.1, < 2.12.6 < 2.12.0-RC.1, 2.12.6

References

https://github.com/nats-io/nats-server/security/advisorie...
x_refsource_CONFIRM
https://advisories.nats.io/CVE/secnote-2026-07.txt
x_refsource_MISC

CVSS V3.1

Score:
7.1
Severity:
HIGH
Confidentiality:
Low
Integrity:
High
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.