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. The
‘aws_tls_ctx_options_override_default_trust_store_*’ function within the
aws-c-io submodule has been updated to address this behavior. This issue
affects: Amazon Web Services AWS IoT Device SDK v2 for Java versions prior
to 1.5.0 on macOS. Amazon Web Services AWS IoT Device SDK v2 for Python
versions prior to 1.7.0 on macOS. Amazon Web Services AWS IoT Device SDK v2
for C++ versions prior to 1.14.0 on macOS. Amazon Web Services AWS IoT
Device SDK v2 for Node.js versions prior to 1.6.0 on macOS. Amazon Web
Services AWS-C-IO 0.10.7 on macOS.