Due to a mistake in libcurl's WebSocket code, a malicious server can send a
particularly crafted packet which makes libcurl get trapped in an endless
busy-loop.
There is no other way for the application to escape or exit this loop other
than killing the thread/process.
This might be used to DoS libcurl-using application.
libcurl accidentally skips the certificate verification for QUIC connections when connecting to a host specified as an IP address in the URL. Therefore, it does not detect impostors or man-in-the-middle attacks.
libcurl supports *pinning* of the server certificate public key for HTTPS transfers. Due to an omission, this check is not performed when connecting with QUIC for HTTP/3, when the TLS backend is wolfSSL. Documentation says the option works with wolfSSL, failing to specify that it does not for QUIC and HTTP/3. Since pinning makes the transfer succeed if the pin is fine, users could unwittingly connect to an impostor server without noticing.