CVE-2026-33249: NATS Message Tracing Can Be Redirected Vulnerability

MODERATE
Advisory Identifier: GHSA-8m2x-3m6q-6w8j
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CVSS 4.3
CWE-863
Published
Advisory Summary

CVE-2026-33249 is a MODERATE (CVSS 4.3) message tracing can be redirected vulnerability (CWE-863: Incorrect Authorization) affecting NATS libraries in the Go ecosystem. The issue involves message tracing can be redirected to arbitrary subject. Remediation is available by upgrading affected packages to version 2.11.15, 2.12.6.

CVE-2026-33249 at a Glance

CVE Identifier CVE-2026-33249
GHSA Identifier GHSA-8m2x-3m6q-6w8j
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-863: Incorrect Authorization
Affected Product NATS
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-33249

To remediate this vulnerability, upgrade all affected NATS dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/nats-io/nats-server/v2 fixed: 2.11.15 
Upgrade github.com/nats-io/nats-server/v2 to 2.11.15
github.com/nats-io/nats-server/v2 fixed: 2.12.6 
Upgrade github.com/nats-io/nats-server/v2 to 2.12.6
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/nats-io/nats-server/v2

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-33249, inspect your project dependencies for NATS:

inspect dependencies for github.com/nats-io/nats-server/v2

Analyze the terminal output to locate any version of NATS in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.11.15), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-863: Incorrect Authorization, where the product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. In NATS, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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.

CVE-2026-33249 Affected NATS Versions

2 component(s)
Fixed Versions:
2.11.152.12.6
Product / Package Ecosystem Affected Versions Fixed Version
github.com/nats-io/nats-server/v2
golang/github.com/nats-io/nats-server/v2
Go
≥ 2.11.0
< 2.11.15
2.11.15
github.com/nats-io/nats-server/v2
golang/github.com/nats-io/nats-server/v2
Go
≥ 2.12.0-preview.1
< 2.12.6
2.12.6

References

GitHub Advisory / Wiki ADVISORY
https://github.com/nats-io/nats-server/security/advisories/GHSA-8m2x-3m6q-6w8j
NVD — CVE-2026-33249 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33249
NATS Security Information SECURITY
https://advisories.nats.io/CVE/secnote-2026-15.txt
NATS Source Repository REPOSITORY
https://github.com/nats-io/nats-server

Frequently Asked Questions

What is CVE-2026-33249?
CVE-2026-33249 is a security vulnerability in NATS involving Message tracing can be redirected to arbitrary subject under CWE-863: Incorrect Authorization.
Which NATS versions are affected?
Affected versions include releases prior to 2.11.15, 2.12.6 across affected packages: github.com/nats-io/nats-server/v2.
What version fixes CVE-2026-33249?
Upgrading to 2.11.15, 2.12.6 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/nats-io/nats-server/v2 affected?
Yes, github.com/nats-io/nats-server/v2 is affected in releases prior to 2.11.15, 2.12.6. Upgrade your dependency to 2.11.15, 2.12.6 or later.
What is the CVSS score of CVE-2026-33249?
CVE-2026-33249 has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2026-33249?
CVE-2026-33249 is classified under CWE-863: Incorrect Authorization (The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.).
How can I check Go dependencies for CVE-2026-33249?
Run the dependency tree command: 'inspect dependencies for github.com/nats-io/nats-server/v2'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-8m2x-3m6q-6w8j",
  "modified" : "2026-03-25T21:31:40Z",
  "published" : "2026-03-24T20:37:08Z",
  "aliases" : [ "CVE-2026-33249" ],
  "summary" : "NATS: Message tracing can be redirected to arbitrary subject",
  "details" : "### Background\n\nNATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.\n\nThe nats-server supports telemetry on messages, using the per-message NATS headers.\n\n### Problem Description\n\nA 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.\n\nThe payload is a valid trace message and not chosen by the attacker.\n\n### Affected Versions\n\nAny version before v2.12.6 or v2.11.15\n\n### Workarounds\n\nNone.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/nats-io/nats-server/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.11.0"
      }, {
        "fixed" : "2.11.15"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/nats-io/nats-server/v2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.12.0-preview.1"
      }, {
        "fixed" : "2.12.6"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/nats-io/nats-server/security/advisories/GHSA-8m2x-3m6q-6w8j"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33249"
  }, {
    "type" : "WEB",
    "url" : "https://advisories.nats.io/CVE/secnote-2026-15.txt"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/nats-io/nats-server"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-863" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-24T20:37:08Z",
    "nvd_published_at" : "2026-03-25T21:16:47Z"
  }
}