CVE-2026-33215
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedNATS-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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe vulnerability allows session and message hijacking through manipulation of MQTT Client IDs in the NATS-Server's MQTT client interface. An attacker with the ability to connect to the MQTT broker could potentially impersonate existing clients or intercept messages by using a crafted Client ID, bypassing proper session isolation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 2.0.0, < 2.11.15>= 2.12.0, < 2.12.5CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- 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
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify NATS-Server versionRun `nats-server --version` or check the installed binary versionAffected if version is >= 2.0.0 and < 2.11.15, or >= 2.12.0 and < 2.12.5
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Confirm MQTT gateway is enabledReview NATS-Server configuration file (typically nats.conf) for `mqtt` or `mqtt_port` directives, or check running config with `nats-server -c nats.conf --signal 2` to dump configAffected if MQTT gateway is configured and active (vulnerability only affects MQTT client interface)
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Check for exposed MQTT portsRun `netstat -tlnp | grep -E '1883|8883'` or `ss -tlnp | grep -E '1883|8883'` to see if MQTT ports are listeningAffected if MQTT ports 1883 (plain) or 8883 (TLS) are open and accepting connections from untrusted networks
You are affected if NATS-Server version falls within the vulnerable ranges AND the MQTT gateway is enabled and accessible.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2.11.152.12.5
Upgrade NATS-Server to version 2.11.15 or 2.12.5 to apply the patch. No workarounds are available; immediate upgrade is recommended given the direct session hijacking risk.
2.11.15 or 2.12.5 (depending on your current branch)
- 1. Identify the currently running NATS Server version using 'nats-server --version' or checking the process
- 2. Determine which release branch you're on (2.11.x or 2.12.x) based on your current version
- 3. For 2.11.x branch users: Upgrade to version 2.11.15
- 4. For 2.12.x branch users: Upgrade to version 2.12.5
- 5. Download the appropriate release from https://github.com/nats-io/nats-server/releases
- 6. Stop the running NATS Server instance
- 7. Replace the binary with the new version
- 8. Restart the NATS Server service
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33215 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-33215 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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