dbcve.org
Nats ServerApplication · Linuxfoundation

CVE-2026-58253

HIGH · 8.8 CVSS v3.1 Published 2026-07-08
Fix available
A fix is available. Upgrade to 2.11.16 / 2.12.7 or later.
See remediation →
93/100
Remediation priority · Urgent
No privileges Zero-click Patch available 6 weeks old

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, the cloud and edge native messaging system. Prior to 2.14.0, 2.12.7, and 2.11.16, when no_auth_user was configured, a parser fast path intended for ordinary client connections could also apply to route or leafnode listeners, allowing an unauthenticated peer to bypass inter-server CONNECT authentication and operate with the privileges associated with that connection type. This issue is fixed in versions 2.14.0, 2.12.7, and 2.11.16.

In the news

Third-party coverage
Trending covered by 1 outlet this week · latest 1mo ago

Surfaced from public web coverage — external links open in a new tab.

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

When no_auth_user was configured in NATS Server, a parser optimization for client connections was incorrectly applied to route and leafnode listeners, allowing unauthenticated peers to bypass inter-server CONNECT authentication and operate with the privileges associated with those connection types.

MitigationUpgrade NATS Server to version 2.14.0, 2.12.7, or 2.11.16, or disable the no_auth_user configuration if not required.

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:< 2.11.16>= 2.12.0, < 2.12.7

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
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
High
Availability
Low

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

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. Check NATS Server version
    Run 'nats-server --version' or check the binary version that is running
    Affected if Version is < 2.11.16 OR >= 2.12.0 and < 2.12.7
  2. Verify no_auth_user configuration exists
    Inspect the NATS Server configuration file (typically nats.conf) for the 'no_auth_user' directive
    Affected if The 'no_auth_user' option is present and set to a valid user account
  3. Confirm route or leafnode listeners are configured
    Check the configuration file for 'route' blocks or 'leafnode' blocks, or run 'nats-server -c nats.conf --profile' to list active listeners
    Affected if Route connections (route { ... }) or leafnode connections (leafnode { ... }) are defined in the configuration

If the NATS Server version falls within the affected range AND no_auth_user is configured AND route or leafnode listeners are present, the environment is vulnerable to unauthenticated peer access.

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 2.11.16 / 2.12.7 or later
Fixed in 2.11.162.12.7
Vendor patch github.com →
Interim mitigation

Upgrade NATS Server to version 2.14.0, 2.12.7, or 2.11.16, or disable the no_auth_user configuration if not required.

Recommended fix High confidence

2.14.0 (latest stable release)

  1. 1. Identify the currently running NATS Server version using `nats-server --version`
  2. 2. Determine which release line you are on (2.11.x, 2.12.x, or earlier)
  3. 3. For 2.11.x users: upgrade to version 2.11.16 or later
  4. 4. For 2.12.x users: upgrade to version 2.12.7 or later
  5. 5. For users on versions < 2.11: upgrade to version 2.11.16 or later (or 2.14.0 for latest features)
  6. 6. For users on versions 2.13.x: upgrade to version 2.14.0
  7. 7. After upgrade, verify the server starts successfully and review logs for any authentication-related errors
  8. 8. Test that inter-server (route and leafnode) authentication functions correctly

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
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-58253 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-58253 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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