Viktor Szakats

Setting `CURLOPT AWS SIGV4` to NULL fails to disable SigV4 authentication as expected and documented. Consequently, a subsequent transfer using the same handle continues to send the `Authorization: AWS4-HMAC-SHA256` header to the next specified URL, which leads to the leakage of state information.

The logic handling SASL (Simple Authentication and Security Layer) authentication may clean up the GSASL context twice without clearing the pointer in between. This results in a double-free condition when the `free()` function is called on the same pointer twice.

The issue is related to the exposure of private personal information to an unauthorized actor by leaking credentials in the HTTP Referer: header. libcurl does not strip off user credentials from the URL when automatically populating the `Referer:` HTTP request header field in outgoing HTTP requests, and therefore risks leaking sensitive data to the server that is the target of the second HTTP request. This can be exploited by a remote attacker to gain access to confidential data.