High severity · published Jul 8, 2026
CVE-2026-58253
NATS Server: Route API Auth Bypass
8.8
CVSS
0.4%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L
Attack vector
Adjacent
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
High
Availability
Low
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NA
nats-server · nats-io
< 2.11.16; >= 2.12.0-preview.1, < 2.12.6 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-58253
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-58253
Patch
https://github.com/nats-io/nats-server/commit/7b81dd455ea95960090a84858c7662827948d1b6
Patch
https://github.com/nats-io/nats-server/commit/8b8e1ad4ceed32321e00d4fc6e76be05bc13bca6
Patch
https://github.com/nats-io/nats-server/commit/b86147e81710a52b72a7f7275f91d69f723f5cb3
Release Notes
https://github.com/nats-io/nats-server/releases/tag/v2.11.16
Release Notes
https://github.com/nats-io/nats-server/releases/tag/v2.12.7
Release Notes
https://github.com/nats-io/nats-server/releases/tag/v2.14.0
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