Auth bypass in Linuxfoundation Nats-Server
CVE-2026-33249
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.11.0 and prior to versions 2.11.15 and 2.12.6, a valid client which uses message tracing headers can indicate that the trace messages can be sent to an arbitrary valid subject, including those to which the client does not have publish permission. The payload is a valid trace message and not chosen by the attacker. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.
Vulnerability class: Broken Access Control
EPSS: 0.002 (13.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.
Affected products
- Linuxfoundation Nats-server
- Nats-io Nats-server — versions >= 2.11.0, < 2.11.15, >= 2.12.0-preview.1, < 2.12.6
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
- security-advisories@github.com (x_refsource_MISC, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-33249?
- CVE-2026-33249 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Incorrect Authorization. CVSS score: 4.3/10. Published 2026-03-25.
- How severe is CVE-2026-33249?
- Medium severity. CVSS v3 base score is 4.3 out of 10.