Missing Authorization in nats-server - CVE-2021-3127
Published: March 24, 2021 / Updated: June 30, 2026
Vulnerability identifier: #VU135923
CSH Severity: Low
CVSS v4: 7.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2021-3127
CWE-ID: CWE-862
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to access subjects from another account.
The vulnerability exists due to improper access control in import token permission checking when processing tampered account JWTs with import tokens. A remote user can upload a tampered account JWT that reuses an import token from another account to access subjects from the exporting account.
Exploitation requires deployments where untrusted accounts are able to update the account server with imports, and private exports are in use.
Affected software
nats-server
How to mitigate CVE-2021-3127
Install security update from vendor's website.
nats-server - update to 2.2.0