Incorrect authorization in nats-server - CVE-2026-58211
Published: June 30, 2026
Vulnerability identifier: #VU135931
CSH Severity: Low
CVSS v4: 5.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-58211
CWE-ID: CWE-863
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to gain unauthorized access to permissions assigned to the default user.
The vulnerability exists due to improper access control in the pre-CONNECT fast path when processing a first client operation other than CONNECT. A remote user can send an initial non-CONNECT operation to gain unauthorized access to permissions assigned to the default user.
Only deployments that use no_auth_user together with restrictions such as allowed_connection_types or proxy_required are vulnerable.
Affected software
nats-server
How to mitigate CVE-2026-58211
Install security update from vendor's website.
nats-server - addressed in versions 2.12.12, 2.14.3