NVD / CVE Program· CNA GitHub_M

CVE-2026-33215: NATS is vulnerable to MQTT hijacking via Client ID

Noroxi assessment

Priority: Monitor (action score 26/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.24% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: nats-server (Alpine:v3.23) 2.12.6-r0; nats-server (Debian:14) 2.12.6-1; github.com/nats-io/nats-server/v2 (Go) 2.12.6, 2.11.15.

Low priority for now. Upgrade to nats-server (Alpine:v3.23) 2.12.6-r0; nats-server (Debian:14) 2.12.6-1; github.com/nats-io/nats-server/v2 (Go) 2.12.6, 2.11.15 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.5 · v3.1—No exploit Fix available

Published: Mar 24, 2026
Updated: Jun 17, 2026
EPSS: 0.2% · 15th percentile
CWE: CWE-287

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 26 / 40 · 6.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.2%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 6.5
CNA · GitHub_M: 6.5; agree

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
linuxfoundation	nats-server	cpe:2.3:a:linuxfoundation:nats-server

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linuxfoundation nats-server2.0.0 and later · before 2.11.15
linuxfoundation nats-server2.12.0 and later · before 2.12.5

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

nats-io nats-server
- < 2.11.15, >= 2.12.0-RC.1, < 2.12.6affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.23	nats-server	from 2.0.0 · before 2.12.6-r0	2.12.6-r0
Debian:12	nats-server	from 0	—
Debian:14	nats-server	before 2.12.6-1	2.12.6-1
Go	github.com/nats-io/nats-server	from 0	—
Go	github.com/nats-io/nats-server/v2	from 2.12.0-RC.1 · before 2.12.6	2.12.6
Go	github.com/nats-io/nats-server/v2	before 2.11.15	2.11.15

Same product

linuxfoundation: all records

Other highest-scoring records for the same primary product.

CVE-2020-26892The JWT library in NATS nats-server before 2.1.9 has Incorrect Access Control because of how expired credentials are handled.
40Plan
CVE-2022-28357NATS nats-server 2.2.0 through 2.7.4 allows directory traversal because of an unintended path to a management action from a management accou
39Monitor
CVE-2026-58253NATS Server: Route API Auth Bypass
35Monitor

Published before and after this one in the same product

← EarlierCVE-2023-47090Oct 30, 2023 · NATS nats-server before 2.9.23 and 2.10.x before 2.10.2 has an authentication bypass.
26Monitor
← EarlierCVE-2026-27571Feb 24, 2026 · nats-server websockets are vulnerable to pre-auth memory DoS
30Monitor
Later →CVE-2026-27889Mar 25, 2026 · NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
alpine:nats-server	2.12.6-r0 · Alpine:v3.23	Package registry (OSV)
debian:nats-server	2.12.6-1 · Debian:14	Package registry (OSV)
Go:github.com/nats-io/nats-server/v2	2.11.15	Package registry (OSV)
Go:github.com/nats-io/nats-server/v2	2.12.6	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-58253106 days apartNATS Server: Route API Auth Bypass
35Monitor
CVE-2026-332461 days apartNATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers
21Monitor
CVE-2026-332481 days apartNATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching
16Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

CVE-2026-58213106 days apartNATS Server: MQTT SUBSCRIBE Protocol Injection via Leaf Node/Route Forwarding allows arbitrary NATS command injection
28Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: low · data can be read
Integrity: low · data or configuration can be modified
Availability: none

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: Low
Integrity impact: Low
Availability impact: None

Weakness class (CWE)

CWE-287 · Improper Authentication

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

nvd-primary

Root cause

Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.

The bug in code

The whole CWE-287 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1app.use("/admin", requireSession, adminRouter);
2

3// Route added later skips the middleware
4app.post("/admin-api/config", updateConfig);

Fixed

1const admin = express.Router();
2admin.use(requireSession, requireRole("admin"));
3

4admin.post("/config", updateConfig);
5app.use("/admin", admin);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Change log

Fix✗ → ✓Sep 28, 2026, 10:46 PM UTC

For records you follow, these changes also arrive as notifications. →

References

advisories.nats.io/CVE/secnote-2026-06.tx

Show all references (1 more)

github.com/nats-io/nats-server/security/advisories/GHSA-fcjp-h8cc-6879

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records