Incorrect authorization in nats-server - #VU166205
Published: November 13, 2026
Vulnerability identifier: #VU166205
CSH Severity: Medium
CVSS v4: 8.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-863
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to bypass source-network restrictions and gain unauthorized access to messaging services from a disallowed network.
The vulnerability exists due to incorrect authorization in nats-server's authorization callout handling when accepting user credentials without enforcing their JWT source-network restrictions. A remote user can connect to a reachable server listener using valid callout-issued credentials from a disallowed source to access messaging services despite those restrictions.
The subject permissions returned by the authorization callout remain enforced.
Affected software
nats-server
Remediation
Install security update from vendor's website.
nats-server - addressed in versions 2.14.10, 2.15.3