GHSA-fcjp-h8cc-6879
NATS is vulnerable to MQTT hijacking via Client ID
Quick fix
GHSA-fcjp-h8cc-6879 — github.com/nats-io/nats-server/v2: upgrade to the fixed version with the command below.
go get github.com/nats-io/nats-server/v2@v2.11.15Details
### Background
NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.
The nats-server provides an MQTT client interface.
### Problem Description
Sessions and Messages can by hijacked via MQTT Client ID malfeasance.
### Affected Versions
Any version before v2.12.6 or v2.11.15
### Workarounds
None.
### Resources
* This document is canonically: <https://advisories.nats.io/CVE/secnote-2026-06.txt> * GHSA advisory: <https://github.com/nats-io/nats-server/security/advisories/GHSA-fcjp-h8cc-6879> * MITRE CVE entry: <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-33215>
Are you affected?
Enter the version of the package you're using.
Affected packages
0Fixed in: 2.11.15go get github.com/nats-io/nats-server/v2@v2.11.152.12.0-RC.1Fixed in: 2.12.6go get github.com/nats-io/nats-server/v2@v2.12.6