Skip to content
Log inStart free trial

GHSA-fcjp-h8cc-6879 BIT-nats-2026-33215 CVE-2026-33215 GO-2026-4833

NATS is vulnerable to MQTT hijacking via Client ID

Medium Go
Severity
6.5 / 10
Medium · CVSS 3.1
Exploit chance (EPSS)
0.24%
Chance of exploitation in the next 30 days. Higher than 15.69% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-287 Improper Authentication
Fix
2.11.15
Upgrade github.com/nats-io/nats-server/v2 to this version or later

Description

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

Affected versions

Go

PackageVulnerableFixed in
github.com/nats-io/nats-server
all versions
 No fix yet
github.com/nats-io/nats-server/v2
< 2.11.15
2.11.15
github.com/nats-io/nats-server/v2
>= 2.12.0-RC.1, < 2.12.6
2.12.6
github.com/nats-io/nats-server/v2
< 2.11.15
>= 2.12.0-RC.1, < 2.12.6
2.11.15
2.12.6

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

github.com/nats-io/nats-server/v2 Go → 2.11.15

go
go get github.com/nats-io/nats-server/v2@v2.11.15 && go mod tidy

Severity breakdown

CVSS 3.1 6.5

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

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

Weakness

CWE-287: Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

How to prevent it
  • Architecture and Design: Use an authentication framework or library such as the OWASP ESAPI Authentication feature.

References

Advisories

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-pq2q-rcw4-3hr6
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
High Also affects github.com/nats-io/nats-server
GHSA-3f24-pcvm-5jqc
NATS has mTLS verify_and_map authentication bypass via incorrect Subject DN matching
Medium Also affects github.com/nats-io/nats-server
GHSA-55h8-8g96-x4hj
NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers
Medium Also affects github.com/nats-io/nats-server
GHSA-pwx7-fx9r-hr4h
NATS Server: Incomplete Stripping of Nats-Request-Info Header Allows Identity Spoofing
Medium Also affects github.com/nats-io/nats-server
GHSA-9983-vrx2-fg9c
NATS JetStream has an authorization bypass through its Management API
Medium Also affects github.com/nats-io/nats-server
GHSA-8r68-gvr4-jh7j
NATS is vulnerable to pre-auth DoS through WebSockets client service
Medium Also affects github.com/nats-io/nats-server
GHSA-vprv-35vv-q339
NATS has pre-auth server panic via leafnode handling
High Also affects github.com/nats-io/nats-server
GHSA-jxxm-27vp-c3m5
NATS allows MQTT clients to bypass ACL checks
Medium Also affects github.com/nats-io/nats-server
Is this in your code?

MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.

Check your repos with MergeHarbor