What’s Vulnerable › Vulnerabilities

CVE-2026-58253: NATS Server: Route API Auth Bypass

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-08 · updated 2026-10-25
• Weakness: CWE-287

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.

Affected products

• nats-io nats-server: before 2.11.16; from 2.12.0 before 2.12.7 — fixed in 2.11.16, 2.12.7

How to fix

Upgrade to a fixed version: nats-io nats-server 2.11.16, 2.12.7. Check the vendor advisory for mitigations.

References

• https://github.com/nats-io/nats-server/commit/7b81dd455ea95960090a84858c7662827948d1b6
• https://github.com/nats-io/nats-server/commit/8b8e1ad4ceed32321e00d4fc6e76be05bc13bca6
• https://github.com/nats-io/nats-server/commit/b86147e81710a52b72a7f7275f91d69f723f5cb3
• https://github.com/nats-io/nats-server/releases/tag/v2.11.16
• https://github.com/nats-io/nats-server/releases/tag/v2.12.7
• https://github.com/nats-io/nats-server/releases/tag/v2.14.0
• https://github.com/nats-io/nats-server/security/advisories/GHSA-38x3-76xf-cq45

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