CVE-2021-3127: NATS Server Incorrect Access Control

nats Updated 02 Oct 2025

Summary

06/03/2024

Disclosed on

CVE-2021-3127

CVE

Yes i

Fix available

High

Severity

Not published

CVSS Score

CVE-2021-3127: NATS Server 2.x before 2.2.0 and JWT library before 2.0.1 have Incorrect Access Control because Import Token bindings are mishandled. Affects nats versions >= 2.0.0, < 2.2.0. Fixed in 2.2.0. How to fix ↓

Also tracked for

The same CVE-2021-3127 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.

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Background

NATS Server is a messaging system that provides a lightweight and high-performance solution for communication between distributed systems. It is widely used in cloud-native applications and microservices architectures. This vulnerability affects NATS Server version 2.x before 2.2.0 and the JWT library before 2.0.1. The vulnerability arises due to mishandling of Import Token bindings, leading to incorrect access control.

Vulnerability Detail

The vulnerability allows unauthorized access to NATS Server and JWT library. Attackers can exploit this vulnerability to bypass access controls and gain unauthorized privileges. This can result in unauthorized data access, data manipulation, or even a complete compromise of the affected system. The vulnerability is rated as high severity with a CVSS score of 8.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

How To Fix

Minimum fixed version

2.2.0

This is the first release that contains the fix.

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Workaround

There is no known workaround for this vulnerability. It is essential to apply the recommended fixes by upgrading NATS Server and the JWT library to the specified versions.

Conclusion

NATS Server version 2.x before 2.2.0 and JWT library before 2.0.1 are vulnerable to an incorrect access control issue. This can lead to unauthorized access and potential compromise of the affected system. It is crucial to upgrade NATS Server and the JWT library to the recommended versions to mitigate this vulnerability. For further support on vulnerability remediation, please contact DevNack.com.

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