Improper Authentication in nats-server - CVE-2026-58253
Published: June 30, 2026
Vulnerability identifier: #VU135926
CSH Severity: High
CVSS v4: 7.2 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-58253
CWE-ID: CWE-287
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass authentication and gain privileges associated with inter-server connection types.
The vulnerability exists due to improper authentication in route or leafnode listeners when processing connections before the inter-server CONNECT authentication flow completes. A remote attacker can connect to an affected listener and exploit the parser fast path to bypass authentication and gain privileges associated with inter-server connection types.
The issue occurs when no_auth_user is configured.
Affected software
nats-server
How to mitigate CVE-2026-58253
Install security update from vendor's website.
nats-server - addressed in versions 2.11.16, 2.12.7, 2.14.0