A user can tell curl >= 7.20.0 and <= 7.78.0 to require a successful upgrade to TLS when speaking to an IMAP, POP3 or FTP server ('--ssl-reqd' on the command line or'CURLOPT_USE_SSL' set to 'CURLUSESSL_CONTROL' or 'CURLUSESSL_ALL' withlibcurl). This requirement could be bypassed if the server would return a properly crafted but perfectly legitimate response.This flaw would then make curl silently continue its operations **withoutTLS** contrary to the instructions and expectations, exposing possibly sensitive data in clear text over the network.
https://nvd.nist.gov/vuln/detail/CVE-2021-22946
