CURL-CVE-2023-23914

curl's HSTS functionality fail when multiple URLs are requested serially.

Using its HSTS support, curl can be instructed to use HTTPS instead of using an insecure clear-text HTTP step even when HTTP is provided in the URL. This HSTS mechanism would however surprisingly be ignored by subsequent transfers when done on the same command line because the state would not be properly carried on.

Reproducible like this:

curl --hsts "" https://curl.se http://curl.se

The first URL returns HSTS information that the second URL fails to take advantage of.