What’s Vulnerable › Vulnerabilities

CVE-2026-33249: NATS: Message tracing can be redirected to arbitrary subject

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-25 · updated 2026-06-17
• Weakness: CWE-863

Description

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.

Affected products

• nats-io nats-server: from 2.11.0 before 2.11.15; from 2.12.0 before 2.12.6 — fixed in 2.11.15, 2.12.6

How to fix

Upgrade to a fixed version: nats-io nats-server 2.11.15, 2.12.6. Check the vendor advisory for mitigations.

References

• https://advisories.nats.io/CVE/secnote-2026-15.txt
• https://github.com/nats-io/nats-server/security/advisories/GHSA-8m2x-3m6q-6w8j

Get alerted when CVE-2026-33249 or the next vulnerability affects your stack