CVE-2021-40831 – Missing SNI validation and inconsistent CA override function behavior within AWS IoT Device SDKs on Apple devices

https://notcve.org/view.php?id=CVE-2021-40831

The AWS IoT Device SDK v2 for Java, Python, C++ and Node.js appends a user supplied Certificate Authority (CA) to the root CAs instead of overriding it on macOS systems. Additionally, SNI validation is also not enabled when the CA has been “overridden”. TLS handshakes will thus succeed if the peer can be verified either from the user-supplied CA or the system’s default trust-store. Attackers with access to a host’s trust stores or are able to compromise a certificate authority already in the host's trust store (note: the attacker must also be able to spoof DNS in this case) may be able to use this issue to bypass CA pinning. An attacker could then spoof the MQTT broker, and either drop traffic and/or respond with the attacker's data, but they would not be able to forward this data on to the MQTT broker because the attacker would still need the user's private keys to authenticate against the MQTT broker. • https://github.com/aws/aws-iot-device-sdk-cpp-v2 https://github.com/aws/aws-iot-device-sdk-java-v2 https://github.com/aws/aws-iot-device-sdk-js-v2 https://github.com/aws/aws-iot-device-sdk-python-v2 https://github.com/awslabs/aws-c-io • CWE-295: Improper Certificate Validation •