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HIGH severity

CVE-2026-33247 — nats-server

HIGH

CVE-2026-33247 is a high-severity (CVSS 7.4) CWE-215 vulnerability in github.com/nats-io/nats-server/v2. A fix is available for github.com/nats-io/nats-server/v2 — see the affected versions and patch details below.

NATS credentials are exposed in monitoring port via command-line argv

Also known asBIT-nats-2026-33247GHSA-x6g4-f6q3-fqvvGO-2026-4827
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33247.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs37th percentile — riskier than 37% of all scored CVEsHighest risk
0.00%0.35%0.69%1.04%0.0%0.4%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🐹github.com/nats-io/nats-server/v2🐹github.com/nats-io/nats-server/v2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

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 provides an optional monitoring port, which provides access to sensitive data. The nats-server can take certain configuration options on the command-line instead of requiring a configuration file.

Problem Description

If a nats-server is run with static credentials for all clients provided via argv (the command-line), then those credentials are visible to any user who can see the monitoring port, if that too is enabled.

The /debug/vars end-point contains an unredacted copy of argv.

Patches

Fixed in nats-server 2.12.6 & 2.11.15

Workarounds

The NATS Maintainers are bemused at the concept of someone deploying a real configuration using --pass to avoid a config file, but also enabling monitoring.

Configure credentials inside a configuration file instead of via argv.

Do not enable the monitoring port if using secrets in argv.

Best practice remains to not expose the monitoring port to the Internet, or to untrusted network sources.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/nats-io/nats-server/v2all versions2.11.15go get github.com/nats-io/nats-server/v2@v2.11.15
🐹Gogithub.com/nats-io/nats-server/v2≥ 2.12.0-RC.1&&< 2.12.62.12.6go get github.com/nats-io/nats-server/v2@v2.12.6

Affected Products

1 product · 2 configurations
Application
nats-serverlinuxfoundation
≥ 2.12.0 && < 2.12.6
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/nats-io/nats-server/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/nats-io/nats-server/v2 to 2.11.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33247 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant
Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for CVE-2026-33247 (CC BY 4.0)
ProductFixed inAdvisory
Multicluster Global Hub 1.4.9multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1779579439RHSA-2026:22347
Multicluster Global Hub 1.6.5multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1780167118RHSA-2026:23345
Red Hat multicluster global hub 1.5.3multicluster-globalhub/multicluster-globalhub-grafana-rhel9:1778867753RHSA-2026:21769

Frequently Asked Questions

### 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 provides an optional monitoring port, which provides access to sensitive data. The nats-server can take certain configuration options on the command-line instead of requiring a configuration file. ### Problem Description If a nats-server is run with static credentials for all clients provided via argv (the command-line), then those credentials are visible to any user who can see the monitoring port, if that too is
O3 Security · Impact-Aware SCA

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CVE-2026-33247: nats-server — Fixed in 2.11.15