---
id: CVE-2026-33217
title: >-
  NATS-Server is a High-Performance server for NATS.io, a cloud and edge native
  messaging system
summary: >-
  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 M…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N'
cwe:
  - CWE-863
  - CWE-425
vendor: linuxfoundation
product: nats-server
affected:
  - nats-server < 2.11.15
  - 'nats-server >= 2.12.0, < 2.12.6'
patched:
  - nats-server 2.12.6
published: '2026-03-25'
updated: '2026-09-09'
sourceUpdated: '2026-09-09T13:19:23.763'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-33217'
references:
  - url: 'https://advisories.nats.io/CVE/secnote-2026-07.txt'
    label: security-advisories@github.com
  - url: >-
      https://github.com/nats-io/nats-server/security/advisories/GHSA-jxxm-27vp-c3m5
    label: security-advisories@github.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:21769'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:22347'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/errata/RHSA-2026:23345'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://access.redhat.com/security/cve/CVE-2026-33217'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2451446'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33217.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-33217'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-33217'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-03-25T20:07:59.832372Z'
epss: 0.00259
epssPercentile: 0.17935
scores:
  nvd: 7.1
  vendor: 8.1
  cna: 7.1
ingestedAt: '2026-07-20T12:38:40.691Z'
---

## Overview

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.

## Affected

- `nats-server < 2.11.15`
- `nats-server >= 2.12.0, < 2.12.6`

## Remediation

Upgrade past the affected range:

- `nats-server 2.12.6`

## Vendor advisories

- **RHSA-2026:22347** · Red Hat · fixed in: Multicluster Global Hub 1.4.5 · released 2026-06-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:22347)
- **RHSA-2026:23345** · Red Hat · fixed in: Multicluster Global Hub 1.6.5 · released 2026-06-04 · [advisory](https://access.redhat.com/errata/RHSA-2026:23345)
- **RHSA-2026:21769** · Red Hat · fixed in: Red Hat multicluster global hub 1.5.3 · released 2026-05-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:21769)