CVE-2026-33215: Github.com/nats io/nats server/v2 NATS Is Vulnerable To MQTT Vulnerability
MODERATECVE-2026-33215 is a MODERATE (CVSS 6.5) nats is vulnerable to mqtt vulnerability (CWE-287: Improper Authentication) affecting Github.com/nats io/nats server/v2 libraries in the Go ecosystem. The issue involves nats is vulnerable to mqtt hijacking via client id. Remediation is available by upgrading affected packages to version 2.11.15, 2.12.6.
CVE-2026-33215 at a Glance
Security Impact
CVSS: 6.5
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L).
How to Fix CVE-2026-33215
To remediate this vulnerability, upgrade all affected Github.com/nats io/nats server/v2 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/nats-io/nats-server/v2 to 2.11.15Upgrade github.com/nats-io/nats-server/v2 to 2.12.6Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/nats-io/nats-server/v2How to Check if You Are Affected
To determine whether your application is affected by CVE-2026-33215, inspect your project dependencies for Github.com/nats io/nats server/v2:
inspect dependencies for github.com/nats-io/nats-server/v2Analyze the terminal output to locate any version of Github.com/nats io/nats server/v2 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.11.15), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. In Github.com/nats io/nats server/v2, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-33215 Affected Github.com/nats io/nats server/v2 Versions
2 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/nats-io/nats-server/v2
|
Go |
< 2.11.15
|
2.11.15
|
|
github.com/nats-io/nats-server/v2
|
Go |
≥ 2.12.0-RC.1
< 2.12.6
|
2.12.6
|
References
Frequently Asked Questions
What is CVE-2026-33215?
Which Github.com/nats io/nats server/v2 versions are affected?
What version fixes CVE-2026-33215?
Is github.com/nats-io/nats-server/v2 affected?
What is the CVSS score of CVE-2026-33215?
What CWE is associated with CVE-2026-33215?
How can I check Go dependencies for CVE-2026-33215?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-fcjp-h8cc-6879",
"modified" : "2026-03-27T20:55:01Z",
"published" : "2026-03-24T21:39:52Z",
"aliases" : [ "CVE-2026-33215" ],
"summary" : "NATS is vulnerable to MQTT hijacking via Client ID",
"details" : "### Background\n\nNATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.\n\nThe nats-server provides an MQTT client interface.\n\n### Problem Description\n\nSessions and Messages can by hijacked via MQTT Client ID malfeasance.\n\n### Affected Versions\n\nAny version before v2.12.6 or v2.11.15\n\n### Workarounds\n\nNone.\n\n### Resources\n\n * This document is canonically: <https://advisories.nats.io/CVE/secnote-2026-06.txt>\n * GHSA advisory: <https://github.com/nats-io/nats-server/security/advisories/GHSA-fcjp-h8cc-6879>\n * MITRE CVE entry: <https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-33215>",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/nats-io/nats-server/v2"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "2.11.15"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/nats-io/nats-server/v2"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "2.12.0-RC.1"
}, {
"fixed" : "2.12.6"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/nats-io/nats-server/security/advisories/GHSA-fcjp-h8cc-6879"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33215"
}, {
"type" : "WEB",
"url" : "https://advisories.nats.io/CVE/secnote-2026-06.tx"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/nats-io/nats-server"
}, {
"type" : "WEB",
"url" : "https://pkg.go.dev/vuln/GO-2026-4833"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-287" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-24T21:39:52Z",
"nvd_published_at" : "2026-03-24T21:16:28Z"
}
}