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Nats ServerApplication · Linuxfoundation

CVE-2026-33246

MEDIUM · 5.4 CVSS v3.1 Published 2026-03-25
Fix available
A fix is available. Upgrade to 2.11.15 / 2.12.6 or later.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The 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. A 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. Prior to versions 2.11.15 and 2.12.6, NATS clients relying upon the Nats-Request-Info: header could be spoofed. This does 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. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In NATS-Server prior to versions 2.11.15 and 2.12.6, the Nats-Request-Info header could be spoofed because leafnodes connecting to a nats-server were not fully validated unless the system account was properly bridged. This allowed identity claims to propagate unchecked to NATS clients that rely on this header for trust decisions.

MitigationUpgrade nats-server to version 2.11.15 or 2.12.6. No workarounds are available; clients using Nats-Request-Info header for trust decisions should verify their implementation after patching.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nats ServerApplication
Affected:< 2.11.15>= 2.12.0, < 2.12.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the installed NATS Server version
    Run `nats-server --version` or check the nats-server binary/version file to determine the exact version number
    Affected if The version is less than 2.11.15, or greater than or equal to 2.12.0 but less than 2.12.6
  2. Determine if leafnodes are configured
    Review the NATS Server configuration file (typically nats.conf) for any `leafnodes` block or section definition
    Affected if Leafnodes are defined in the configuration, as the vulnerability affects leafnode connections to the server
  3. Check if system account bridging is configured
    Examine the configuration for proper system account bridging setup, typically in the accounts or system section of the configuration
    Affected if The system account is not properly bridged or bridging is not configured at all
  4. Identify if clients rely on Nats-Request-Info header
    Review client application code or configuration that consumes NATS messages to determine if the Nats-Request-Info header is used for authentication or trust decisions
    Affected if Any client application uses the Nats-Request-Info header for trust or authentication decisions

You are affected if your NATS Server version falls within the vulnerable range AND leafnodes are in use AND the system account is not properly bridged AND clients rely on the Nats-Request-Info header for trust decisions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2.11.15 / 2.12.6 or later
Fixed in 2.11.152.12.6
Interim mitigation

Upgrade nats-server to version 2.11.15 or 2.12.6. No workarounds are available; clients using Nats-Request-Info header for trust decisions should verify their implementation after patching.

Recommended fix High confidence

2.11.15 or 2.12.6 (or later stable release)

  1. 1. Identify the currently installed NATS Server version using `nats-server --version` or checking the service configuration
  2. 2. If running version 2.11.x: upgrade to version 2.11.15 or later
  3. 3. If running version 2.12.0-2.12.5: upgrade to version 2.12.6 or later
  4. 4. Download the appropriate version from https://github.com/nats-io/nats-server/releases
  5. 5. Stop the NATS Server service
  6. 6. Replace the nats-server binary or update the container image
  7. 7. Restart the NATS Server service
  8. 8. Verify the new version is running with `nats-server --version`
Caveat Review NATS Server release notes for any changes between your current version and target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Nats Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,060
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-33246 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data