CVE-2021-40831 Explained : Impact and Mitigation

This CVE covers a vulnerability in the AWS IoT Device SDKs for Java, Python, C++, Node.js, and AWS-C-IO on macOS devices.

Understanding CVE-2021-40831

This CVE identifies a security issue in the AWS IoT Device SDKs that can be exploited by attackers to bypass CA pinning on Apple devices.

What is CVE-2021-40831?

The AWS IoT Device SDKs append a user-supplied Certificate Authority (CA) to the root CAs on macOS systems, not overriding it. This behavior allows attackers to potentially bypass CA pinning and spoof the MQTT broker.

The Impact of CVE-2021-40831

The vulnerability has a CVSS base score of 6.3 (Medium severity) with high impact on confidentiality, integrity, and availability. Attackers with access to trust stores could manipulate TLS handshakes.

Technical Details of CVE-2021-40831

This section delves into the specifics of the vulnerability.

Vulnerability Description

The issue lies in the improper handling of CA overrides in the AWS IoT Device SDKs on macOS, potentially enabling CA pinning bypass.

Affected Systems and Versions

AWS IoT Device SDK v2 for Java < 1.5.0
AWS IoT Device SDK v2 for Python < 1.7.0
AWS IoT Device SDK v2 for C++ < 1.14.0
AWS IoT Device SDK v2 for Node.js < 1.6.0
AWS-C-IO 0.10.7

Exploitation Mechanism

Attackers can exploit this by compromising a certificate authority in the host's trust store to spoof a broker without forwarding data to the MQTT broker.

Mitigation and Prevention

Here are the steps to address and prevent this vulnerability.

Immediate Steps to Take

Update to the latest versions of the affected AWS IoT Device SDKs.

Long-Term Security Practices

Regularly review and update trust stores and certificates.
Implement strong DNS spoofing prevention measures.
Educate users on secure MQTT broker authentication.

Patching and Updates

Ensure systems are regularly patched with the latest versions of the AWS IoT Device SDKs to mitigate this vulnerability.