CVE-2026-58253: CWE-287: Improper Authentication in nats-io nats-server
NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.0, 2.12.7, and 2.11.16, when no_auth_user was configured, a parser fast path intended for ordinary client connections could also apply to route or leafnode listeners, allowing an unauthenticated peer to bypass inter-server CONNECT authentication and operate with the privileges associated with that connection type. This issue is fixed in versions 2.14.0, 2.12.7, and 2.11.16.
AI Analysis
Technical Summary
CVE-2026-58253 is an improper authentication vulnerability (CWE-287) in nats-io nats-server. When the no_auth_user option is configured, a parser fast path intended for ordinary client connections also applies to route or leafnode listeners. This allows an unauthenticated peer to bypass inter-server CONNECT authentication and operate with the privileges of that connection type. The vulnerability affects versions prior to 2.14.0, 2.12.7, and 2.11.16 and is fixed in these versions.
Potential Impact
An unauthenticated attacker can bypass inter-server authentication mechanisms and gain unauthorized access with the privileges of route or leafnode connections. This can lead to unauthorized information disclosure, modification, or disruption of service within the NATS messaging system. The CVSS 3.1 score of 8.8 reflects high severity with low attack complexity, no privileges required, no user interaction, and a scope change.
Mitigation Recommendations
Upgrade nats-server to version 2.14.0, 2.12.7, or 2.11.16 or later to remediate this vulnerability. These versions contain the official fix that prevents authentication bypass when no_auth_user is configured. No other mitigations are indicated by the vendor advisory.
CVE-2026-58253: CWE-287: Improper Authentication in nats-io nats-server
Description
NATS Server is a high-performance server for NATS.io, the cloud and edge native messaging system. Prior to 2.14.0, 2.12.7, and 2.11.16, when no_auth_user was configured, a parser fast path intended for ordinary client connections could also apply to route or leafnode listeners, allowing an unauthenticated peer to bypass inter-server CONNECT authentication and operate with the privileges associated with that connection type. This issue is fixed in versions 2.14.0, 2.12.7, and 2.11.16.
CVSS v3.1
Score 8.8high
Affected software
pkg:github/nats-io/nats-serverRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-58253 is an improper authentication vulnerability (CWE-287) in nats-io nats-server. When the no_auth_user option is configured, a parser fast path intended for ordinary client connections also applies to route or leafnode listeners. This allows an unauthenticated peer to bypass inter-server CONNECT authentication and operate with the privileges of that connection type. The vulnerability affects versions prior to 2.14.0, 2.12.7, and 2.11.16 and is fixed in these versions.
Potential Impact
An unauthenticated attacker can bypass inter-server authentication mechanisms and gain unauthorized access with the privileges of route or leafnode connections. This can lead to unauthorized information disclosure, modification, or disruption of service within the NATS messaging system. The CVSS 3.1 score of 8.8 reflects high severity with low attack complexity, no privileges required, no user interaction, and a scope change.
Mitigation Recommendations
Upgrade nats-server to version 2.14.0, 2.12.7, or 2.11.16 or later to remediate this vulnerability. These versions contain the official fix that prevents authentication bypass when no_auth_user is configured. No other mitigations are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-29T21:54:30.330Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4eafe9c9d9e3dbe3adea86
Added to database: 07/08/2026, 20:15:37 UTC
Last enriched: 07/16/2026, 10:13:21 UTC
Last updated: 08/22/2026, 22:52:15 UTC
Views: 80
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