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CVE-2026-58211

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

Published: Jul 8, 2026Updated: Jul 9, 2026 Sources: CVE List NVDCWE-863
5.4MEDIUM
NVD MITRE
EPSS Score
0.2%
Top 89.1%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Workaround Only
Self-Check
Not available

Description

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:LI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:LConfidentiality
Low
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-863

Affected Products

nats-io
oss-project
nats-serverOn-prem
Databases / cache-message-queue
linuxfoundation
oss-project·USaka pytorch, yocto, everest
nats-serverOn-premDatabase
AI / ML / vector-db-rag

Exploitability

Workaround Available

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
View detailed technique mapping

References

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

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