MGASA-2024-0360

When curl is asked to use HSTS, the expiry time for a subdomain might overwrite a parent domain's cache entry, making it end sooner or later than otherwise intended. This affects curl using applications that enable HSTS and use URLs with the insecure HTTP:// scheme and perform transfers with hosts like x.example.com as well as example.com where the first host is a subdomain of the second host. This flaw also affects the curl command line tool. When triggered, this is a potential minor DoS security problem when trying to use HTTPS when that no longer works or a cleartext transmission of data that was otherwise intended to possibly be protected. This update fixes the issue so subdomains cannot affect the HSTS cache of a parent domain.