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Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

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

High 8.8

In plain English

A high-severity improper authentication in nats-server from nats-io. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High
Exploit odds (30 days)0.4%top 69.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nats-serverno fix listedDEBIAN-CVE-2026-58253
Debian:13nats-serverno fix listedDEBIAN-CVE-2026-58253
Debian:14nats-server2.14.1-1DEBIAN-CVE-2026-58253
Ubuntu:24.04:LTSnats-serverno fix listedUBUNTU-CVE-2026-58253
Ubuntu:25.10nats-serverno fix listedUBUNTU-CVE-2026-58253

Affected products (as reported)

VendorProductVersions
nats-io nats-server < 2.11.16>= 2.12.0-preview.1, < 2.12.6

Weakness: CWE-287 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L

References