curl: Use-after-free in `curl_easy_duphandle()` with HTTP/2 stream-dependency tree

Hi all, We've found an issue in lib/easy.c where curleasyduphandle shallow-copies set.priority, so the original and the duplicate end up holding two independent pointer-typed variables that both reference the same heap-allocated Curldataprionode chain. Freeing the chain from one side leaves the...