CVE-2026-58211Network attack vector

Unauthenticated permission gain via pre-CONNECT parser path

Published Jul 8, 2026 · Updated Jul 8, 2026

Incorrect authorization in NATS Server before 2.12.12 and 2.14.0-RC.1 through 2.14.2 allows remote attackers to gain default-user permissions. When the first client operation is not CONNECT, a parser path registers the client as no_auth_user without enforcing normal user-level connection restrictions. Exploitation requires no_auth_user plus allowed_connection_types or proxy_required, and the consequence is bounded by that user's permissions.

CVSS severity5.4
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in NATS Server before 2.12.12 and 2.14.0-RC.1 through 2.14.2 allows remote attackers to gain default-user permissions. When the first client operation is not CONNECT, a parser path registers the client as no_auth_user without enforcing normal user-level connection restrictions. Exploitation requires no_auth_user plus allowed_connection_types or proxy_required, and the consequence is bounded by that user's permissions.

The record

CVE
CVE-2026-58211
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
NATS
Product
NATS Server
Classifications
CWE-863, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.12.12
  2. Affected versionversion=>= 2.14.0-RC.1, < 2.14.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NATS · NATS Serverversion=< 2.12.12; version=>= 2.14.0-RC.1, < 2.14.3

Published CVSS scores

5.4GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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