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Message tracing can be redirected to arbitrary subject

Moderate
philpennock published GHSA-8m2x-3m6q-6w8j Mar 24, 2026

Package

gomod github.com/nats-io/nats-server/v2 (Go)

Affected versions

>= 2.11.0, <= 2.11.14, <= 2.12.5

Patched versions

2.12.6, 2.11.15

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 supports telemetry on messages, using the per-message NATS headers.

Problem Description

A valid client which uses message tracing headers can indicate that the trace messages can be sent to an arbitrary valid subject, including those to which the client does not have publish permission.

The payload is a valid trace message and not chosen by the attacker.

Affected Versions

Any version before v2.12.6 or v2.11.15

Workarounds

None.

References

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

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

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVE ID

CVE-2026-33249

Weaknesses

No CWEs