CVE-2026-33215

NATS is vulnerable to MQTT hijacking via Client ID

CVSS 3.1 6.5 MEDIUMEUVD CVSS 3.1 6.5 CVSS 3.1 · [email protected] · Secondary 6.5 MEDIUMCVSS 3.1 · [email protected] · Primary 6.5 MEDIUMCVSS_V3 Publisher rating MODERATEFixed by github.com/nats-io/nats-server/v2 2.11.15 Fixed by github.com/nats-io/nats-server/v2 2.12.6osv · severity unknownFixed by github.com/nats-io/nats-server/v2 2.11.15 Fixed by github.com/nats-io/nats-server/v2 2.12.6KEV status unknown

Original advisory

cve-program · CVE-2026-33215

Published

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client ID malfeasance. Versions 2.11.15 and 2.12.5 patch the issue. No known workarounds are available.

Read the publisher's advisory

euvd · EUVD-2026-15017

Published

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nvd · CVE-2026-33215

Published

Read the publisher's advisory

osv · GHSA-fcjp-h8cc-6879

Published

### 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>

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osv · GO-2026-4833

Published

NATS is vulnerable to MQTT hijacking via Client ID in github.com/nats-io/nats-server

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Affected versions, risk and source history

cve-program · CVE-2026-33215

Published

nats-server

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "nats-io",
                    "product": "nats-server",
                    "versions": [
                        {
                            "version": "< 2.11.15",
                            "status": "affected"
                        },
                        {
                            "version": ">= 2.12.0-RC.1, < 2.12.6",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON

euvd · EUVD-2026-15017

Published

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Mar 24, 2026, 8:55:53 PM

dateUpdated: Mar 25, 2026, 1:05:12 PM

4 related source bulletins · separate from aliases

RHSA-2026:22347: Red Hat Security Advisory: Multicluster Global Hub 1.4.5 security update

CVE-2026-4427 · CVE-2026-21728 · CVE-2026-25679 · CVE-2026-27137 · CVE-2026-27889 · CVE-2026-29785 · CVE-2026-32280 · CVE-2026-32281 · CVE-2026-32282 · CVE-2026-32283 · CVE-2026-32285 · CVE-2026-32286 · CVE-2026-33186 · CVE-2026-33215 · CVE-2026-33216 · CVE-2026-33217 · CVE-2026-33218 · CVE-2026-33219 · CVE-2026-33247 · CVE-2026-33413 · CVE-2026-33487 · CVE-2026-33810 · CVE-2026-33813 · CVE-2026-33997 · CVE-2026-34040 · CVE-2026-34986 · CVE-2026-40890 · CVE-2026-41602 · CVE-2026-41603 · CVE-2026-41604 · CVE-2026-41605 · CVE-2026-41606 · CVE-2026-41607 · CVE-2026-41636 · CVE-2026-43869

WID-SEC-W-2026-0858: NATS Server: Mehrere Schwachstellen

CVE-2026-33215 · CVE-2026-33216 · CVE-2026-33217 · CVE-2026-33218 · CVE-2026-33219 · CVE-2026-33222 · CVE-2026-33223 · CVE-2026-33246 · CVE-2026-33247 · CVE-2026-33248 · CVE-2026-33249

RHSA-2026:21769: Red Hat Security Advisory: Multicluster Global Hub 1.5.4 security update

RHSA-2026:23345: Red Hat Security Advisory: Multicluster Global Hub 1.6.2 security update

No normalized affected-package data is projected for this source revision. The original publisher record may contain additional product and version evidence; this does not establish that a package is unaffected.

Original source record · Cite this exact observation · Complete original publisher JSON

nvd · CVE-2026-33215

Published

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Analyzed

Weakness classifications: CWE-287 · CWE-488

Original publisher date fields

published: 2026-03-24T21:16:28.640

lastModified: 2026-06-17T10:37:08.227

1 source CPE criteria · context only

cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*

The original JSON retains the logical configuration operators, exclusions and version bounds.

Original source record · Cite this exact observation · Complete original publisher JSON

osv · GHSA-fcjp-h8cc-6879

Published

github.com/nats-io/nats-server/v2

SEMVER · introduced 0 → fixed 2.11.15

github.com/nats-io/nats-server/v2

SEMVER · introduced 2.12.0-RC.1 → fixed 2.12.6

Original source record · Cite this exact observation · Complete original publisher JSON

osv · GO-2026-4833

Published

github.com/nats-io/nats-server

SEMVER · introduced 0

github.com/nats-io/nats-server/v2

SEMVER · introduced 0 → fixed 2.11.15 → introduced 2.12.0-RC.1 → fixed 2.12.6

Original source record · Cite this exact observation · Complete original publisher JSON