NATS allows MQTT clients to bypass ACL checks

Summary

CVE	CVE-2026-33217
State	PUBLISHED
Assigner	GitHub_M
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-03-25 20:16:32 UTC
Updated	2026-07-20 12:18:40 UTC
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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

Problem Types: CWE-863 | CWE-425 | CWE-863 CWE-863: Incorrect Authorization | CWE-425 Direct Request ('Forced Browsing')

Version	Source	Type	Score	Severity	Vector
3.1	[email protected]	Primary	6.5	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N`
3.1	ADP	CVSS	8.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`
3.1	[email protected]	Secondary	7.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N`
3.1	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	Secondary	8.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`
3.1	CNA	DECLARED	7.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N`

CVSS v3.1 Breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

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

NVD Known Affected Configurations (CPE 2.3)

Type	Vendor	Product	Version	Update	Edition	Language
Application	Linuxfoundation	Nats-server	All	All	All	All

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Nats-io	Nats-server	affected < 2.11.15	Not specified
CNA	Nats-io	Nats-server	affected >= 2.12.0-RC.1, < 2.12.6	Not specified
ADP	Red Hat	Multicluster Global Hub 1.5.4	unaffected 1778867753 * rpm	Not specified
ADP	Red Hat	Multicluster Global Hub 1.6.2	unaffected 1780167118 * rpm	Not specified
ADP	Red Hat	Red Hat Multicluster Global Hub 1.4.3	unaffected 1779579439 * rpm	Not specified
ADP	Red Hat	Red Hat OpenShift Container Platform 4	Not specified	Not specified

References

Reference	Source	Link	Tags
github.com/nats-io/nats-server/security/advisories/GHSA-jxxm-27vp-c3m5	[email protected]	github.com	Vendor Advisory
bugzilla.redhat.com/show_bug.cgi	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	bugzilla.redhat.com
access.redhat.com/security/cve/CVE-2026-33217	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
access.redhat.com/errata/RHSA-2026:21769	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
access.redhat.com/errata/RHSA-2026:23345	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33217.json	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	security.access.redhat.com
access.redhat.com/errata/RHSA-2026:22347	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
advisories.nats.io/CVE/secnote-2026-07.txt	[email protected]	advisories.nats.io	Vendor Advisory
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

Additional Advisory Data

Source	Time	Event
ADP	2026-03-25T20:01:47.815Z	Reported to Red Hat.
ADP	2026-03-25T19:43:40.969Z	Made public.

Solutions

ADP: RHSA-2026:22347: Multicluster Global Hub 1.4.5

ADP: RHSA-2026:23345: Multicluster Global Hub 1.6.2

ADP: RHSA-2026:21769: Red Hat multicluster global hub 1.5.2

Workarounds

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

There are currently no legacy QID mappings associated with this CVE.