Medium severity · published Mar 25, 2026
CVE-2026-33217
NATS allows MQTT clients to bypass ACL checks
6.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 18% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NA
nats-server · nats-io
< 2.11.15; >= 2.12.0-RC.1, < 2.12.6 · source: vendor, NVD
MG
Multicluster Global Hub 1.4.5 · Red Hat
All versions, or not specified · source: CISA
MG
Multicluster Global Hub 1.6.5 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat multicluster global hub 1.5.3 · Red Hat
All versions, or not specified · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33217
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-33217
Vendor Advisory
https://advisories.nats.io/CVE/secnote-2026-07.txt
Vendor Advisory
https://github.com/nats-io/nats-server/security/advisories/GHSA-jxxm-27vp-c3m5
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:21769
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:22347
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:23345
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-33217
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