Auth bypass in Linuxfoundation Nats-Server
CVE-2026-58211
NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.3 and 2.12.12, a client could be registered as the configured no_auth_user through a parser path used when the first client operation was not CONNECT, bypassing user-level connection restrictions such as allowed_connection_types or proxy_required that normal authentication would apply. This issue is fixed in versions 2.14.3 and 2.12.12.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (20.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 20th percentile — 20.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Linuxfoundation Nats-Server
- Nats-Io Nats-Server — versions < 2.12.12, >= 2.14.0-RC.1, < 2.14.3
Weakness classification (CWE)
References
- github.com/nats-io/nats-server/security/advisories/GHSA-hmmp-q8cx-v964 (Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-58211?
- CVE-2026-58211 is a medium-severity vulnerability in Linuxfoundation Nats-Server, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-07-08.
- How severe is CVE-2026-58211?
- Medium severity. CVSS v3 base score is 5.4 out of 10.