CVE-2026-58211 — NATS Server: `no_auth_user` pre-CONNECT fast path bypasses user connection restrictions

CVE-2026-58211

NATS Server: `no_auth_user` pre-CONNECT fast path bypasses user connection restrictions PUBLISHED

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
nats-io / nats-server	affected < 2.12.12; affected >= 2.14.0-RC.1, < 2.14.3

CWE

CWE-863

References

https://github.com/nats-io/nats-server/security/advisories/GHSA-hmmp-q8cx-v964

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.