CVE-2026-33246: NATS Leafnode Connections Allow Spoofing Of Vulnerability
MODERATECVE-2026-33246 is a MODERATE (CVSS 6.4) leafnode connections allow spoofing of vulnerability (CWE-287: Improper Authentication) affecting NATS libraries in the Go ecosystem. The issue involves leafnode connections allow spoofing of nats-request-info identity headers. Remediation is available by upgrading affected packages to version 2.11.15, 2.12.6.
CVE-2026-33246 at a Glance
Security Impact
CVSS: 6.4
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:C/C:L/I:L/A:N).
How to Fix CVE-2026-33246
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.
Upgrade github.com/nats-io/nats-server/v2 to 2.11.15Upgrade github.com/nats-io/nats-server/v2 to 2.12.6Upgrade github.com/nats-io/nats-server to Latest secure releaseRun 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/v2How to Check if You Are Affected
To determine whether your application is affected by CVE-2026-33246, inspect your project dependencies for NATS:
inspect dependencies for github.com/nats-io/nats-server/v2Analyze 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-287: Improper Authentication, where when an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. 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
CVE-2026-33246 Affected NATS Versions
3 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/nats-io/nats-server/v2
|
Go |
< 2.11.15
|
2.11.15
|
|
github.com/nats-io/nats-server/v2
|
Go |
≥ 2.12.0-RC.1
< 2.12.6
|
2.12.6
|
|
github.com/nats-io/nats-server
|
Go |
|
|
References
Frequently Asked Questions
What is CVE-2026-33246?
Which NATS versions are affected?
What version fixes CVE-2026-33246?
Is github.com/nats-io/nats-server/v2 affected?
Is github.com/nats-io/nats-server affected?
What is the CVSS score of CVE-2026-33246?
What CWE is associated with CVE-2026-33246?
How can I check Go dependencies for CVE-2026-33246?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-55h8-8g96-x4hj",
"modified" : "2026-03-27T22:10:07Z",
"published" : "2026-03-24T21:50:25Z",
"aliases" : [ "CVE-2026-33246" ],
"summary" : "NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers",
"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 allows hub/spoke topologies using \"leafnode\" connections by other nats-servers. NATS messages can have headers.\n\n### Problem Description\n\nThe nats-server offers a `Nats-Request-Info:` message header, providing information about a request. This is supposed to provide enough information to allow for account/user identification, such that NATS clients could make their own decisions on how to trust a message, provided that they trust the nats-server as a broker.\n\nA leafnode connecting to a nats-server is not fully trusted unless the system account is bridged too. Thus identity claims should not have propagated unchecked.\n\nThus NATS clients relying upon the Nats-Request-Info: header could be spoofed.\n\nDoes not directly affect the nats-server itself, but the CVSS Confidentiality and Integrity scores are based upon what a hypothetical client might choose to do with this NATS header.\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:C/C:L/I:L/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/nats-io/nats-server/v2"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "2.11.15"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/nats-io/nats-server/v2"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "2.12.0-RC.1"
}, {
"fixed" : "2.12.6"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/nats-io/nats-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/nats-io/nats-server/security/advisories/GHSA-55h8-8g96-x4hj"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33246"
}, {
"type" : "WEB",
"url" : "https://advisories.nats.io/CVE/secnote-2026-08.txt"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/nats-io/nats-server"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-287", "CWE-290" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-24T21:50:25Z",
"nvd_published_at" : "2026-03-25T20:16:33Z"
}
}