A vulnerability was found in curl. The issue occurs when doing HTTP transfers, where curl might erroneously use the read callback to ask for data to send, even when the `CURLOPT_POSTFIELDS` option has been set if it previously used the same handle to issue a `PUT` request which used that callback. This flaw may surprise the application and cause it to misbehave and either send off the wrong data or use memory after free or similar in the subsequent `POST` request. A vulnerability was found in curl. The issue occurs when curl is told to parse a `.netrc` file for credentials. If that file ends in a line with consecutive non-white space letters and no newline, curl could read past the end of the stack-based buffer, and if the read works, it can write a zero byte beyond its boundary. This issue, in most cases, causes a segfault or similar problem. A denial of service can occur if a malicious user can provide a custom netrc file to an application or otherwise affect its contents. A vulnerability was found in curl. The issue occurs if curl is told to use an HTTP proxy for a transfer with a non-HTTP URL. It sets up the connection to the remote server by issuing a `CONNECT` request to the proxy and then tunnels the rest of the protocol through. An HTTP proxy might refuse this request and instead return a non-200 response code to the client. Due to flaws in the error/cleanup handling, this could trigger a double-free issue in curl if using one of the following schemes in the URL for the transfer: `dict,` `gopher,` `gophers,` `ldap`, `ldaps`, `rtmp`, `rtmps`, `telnet.` A vulnerability was found in curl. The issue occurs because curl's HSTS check can be bypassed to trick it to keep using HTTP. Using its HSTS support, it can instruct curl to use HTTPS directly instead of using an insecure clear-text HTTP step even when HTTP is provided in the URL. This mechanism can be bypassed if the hostname in the given URL uses IDN characters that get replaced with ASCII counterparts as part of the IDN conversion. Like using the character UTF-8 U+3002 instead of the common ASCII full stop `.`