The Apache Pulsar C++ Client does not verify peer TLS certificates when making HTTPS calls for the OAuth2.0 Client Credential Flow, even when tlsAllowInsecureConnection is disabled via configuration. This vulnerability allows an attacker to perform a man in the middle attack and intercept and/or modify the GET request that is sent to the ClientCredentialFlow 'issuer url'. The intercepted credentials can be used to acquire authentication data from the OAuth2.0 server to then authenticate with an Apache Pulsar cluster. An attacker can only take advantage of this vulnerability by taking control of a machine 'between' the client and the server. The attacker must then actively manipulate traffic to perform the attack. The Apache Pulsar Python Client wraps the C++ client, so it is also vulnerable in the same way. This issue affects Apache Pulsar C++ Client and Python Client versions 2.7.0 to 2.7.4; 2.8.0 to 2.8.3; 2.9.0 to 2.9.2; 2.10.0 to 2.10.1; 2.6.4 and earlier. Any users running affect…