CVE-2026-58251Network attack vector

Authenticated message disclosure via queue deny override

Published Jul 8, 2026 · Updated Jul 8, 2026

Improper authorization in NATS.io NATS Server before 2.11.16 and 2.12.0-RC.1 through 2.12.6 allows remote authenticated users to read denied messages. In server/client.go, canSubscribe first records a matching plain subject deny, then incorrectly replaces that denial with a successful queue-name check. Valid credentials and combined plain-subject and queue-specific deny rules are required; a crafted queue subscription exposes messages from a denied subject.

CVSS severity6.5
Medium
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper authorization in NATS.io NATS Server before 2.11.16 and 2.12.0-RC.1 through 2.12.6 allows remote authenticated users to read denied messages. In server/client.go, canSubscribe first records a matching plain subject deny, then incorrectly replaces that denial with a successful queue-name check. Valid credentials and combined plain-subject and queue-specific deny rules are required; a crafted queue subscription exposes messages from a denied subject.

The record

CVE
CVE-2026-58251
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
NATS.io
Product
NATS Server
Classifications
CWE-285
Attack vector
network
Privileges
authenticated

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=< 2.11.16
  2. Affected versionversion=>= 2.12.0-RC.1, < 2.12.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

NATS.io · NATS Serverversion=< 2.11.16; version=>= 2.12.0-RC.1, < 2.12.7

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-285Improper Authorization

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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