Auth bypass in Linuxfoundation Nats-Server
CVE-2026-33215
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The nats-server provides an MQTT client interface. Prior to versions 2.11.15 and 2.12.5, Sessions and Messages can by hijacked via MQTT Client ID malfeasance. Versions 2.11.15 and 2.12.5 patch the issue. No known workarounds are available.
Vulnerability class: Broken Authentication
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L.
EPSS exploit prediction
EPSS: 0.003 (19.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 19.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000
Affected products
- Linuxfoundation Nats-Server
- Nats-Io Nats-Server — versions < 2.11.15, >= 2.12.0-RC.1, < 2.12.6
Weakness classification (CWE)
References
- github.com/nats-io/nats-server/security/advisories/GHSA-fcjp-h8cc-6879 (Vendor Advisory)
- advisories.nats.io/CVE/secnote-2026-06.tx (Broken Link)
Frequently asked questions
- What is CVE-2026-33215?
- CVE-2026-33215 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Improper Authentication. CVSS score: 6.5/10. Published 2026-03-24.
- How severe is CVE-2026-33215?
- Medium severity. CVSS v3 base score is 6.5 out of 10.