CVE-2026-33247

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.

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.

CVE-2026-33247 has a CVSS score of 7.4 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.11.15, 2.12.6); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-33247? CVE-2026-33247 is a high-severity security vulnerability in github.com/nats-io/nats-server/v2 (go), affecting versions < 2.11.15. It is fixed in 2.11.15, 2.12.6.
2. How severe is CVE-2026-33247? CVE-2026-33247 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/nats-io/nats-server/v2 are affected by CVE-2026-33247? github.com/nats-io/nats-server/v2 (go) versions < 2.11.15 is affected.
4. Is there a fix for CVE-2026-33247? Yes. CVE-2026-33247 is fixed in 2.11.15, 2.12.6. Upgrade to this version or later.
5. Is CVE-2026-33247 exploitable, and should I be worried? Whether CVE-2026-33247 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-33247 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-33247?
   • Upgrade github.com/nats-io/nats-server/v2 to 2.11.15 or later
   • Upgrade github.com/nats-io/nats-server/v2 to 2.12.6 or later